U.S. patent application number 09/758985 was filed with the patent office on 2001-07-26 for brake lining wear detection apparatus.
Invention is credited to Ishida, Toshiyuki, Kaneko, Junya, Ohba, Mitsuyoshi, Yoshida, Shin.
Application Number | 20010009212 09/758985 |
Document ID | / |
Family ID | 18536787 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009212 |
Kind Code |
A1 |
Ohba, Mitsuyoshi ; et
al. |
July 26, 2001 |
Brake lining wear detection apparatus
Abstract
In the expander 50 in a drum brake, when the brake is activated,
the sleeve 56 is extended in the lateral directions in the drawing
by the wedge 52 inserted within the housing 51, and the shoe
engaged with the clip 58 is swung to press the lining 23 against
the drum, and friction braking is performed. When the lining 23
wears away and the amount of movement of the sleeve 56 increases,
the sleeve 56 is rotated by reciprocal action with a drive ring 62
that is engaged with the periphery of the sleeve and, thereby, the
pressing screw 57 screwed thereon comes out by the amount of the
increase of movement (the amount of wear on the lining). A flat
surface 56c is formed on the periphery of the sleeve and the
detecting head 80 of the displacement detection apparatus detects
the rotation of the sleeve 56. The controller performs a warning
operation with the warning means when the cumulative number
rotations of the sleeve 56 has reached a prescribed number of
rotations.
Inventors: |
Ohba, Mitsuyoshi; (Tokyo,
JP) ; Ishida, Toshiyuki; (Tokyo, JP) ;
Yoshida, Shin; (Tokyo, JP) ; Kaneko, Junya;
(Tokyo, JP) |
Correspondence
Address: |
ROBERT W. J. USHER
PATENT AGENT
1133 BROADWAY, #1515
NEW YORK
NY
10010
|
Family ID: |
18536787 |
Appl. No.: |
09/758985 |
Filed: |
January 11, 2001 |
Current U.S.
Class: |
188/1.11W |
Current CPC
Class: |
F16D 65/56 20130101;
F16D 65/22 20130101; F16D 2125/32 20130101; F16D 65/568 20130101;
F16D 66/025 20130101; F16D 2121/14 20130101; F16D 2125/66 20130101;
F16D 65/183 20130101 |
Class at
Publication: |
188/1.11W |
International
Class: |
F16D 066/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2000 |
JP |
2000-008529 |
Claims
What is claimed is:
1. A brake lining wear detection apparatus for detecting wear on
brake linings in a friction brake which comprises: a lining member
on which a brake lining is provided; a brake member that is pressed
and braked by said brake lining when the brake is activated; a
pressing member for pressing said brake lining onto said brake
member when the brake is activated; means for generating pressing
force for causing said pressing member to exert a pressing force; a
transmission member that screws onto said pressing member between
said pressing member and said means for generating pressing force
and is disposed rotatably about this screw shaft, and which
transmits the pressing force generated by said means for generating
pressing force to said pressing member in the direction of said
screw shaft; and an adjustment mechanism which rotates said
transmission member about said screw axis to cause the pressing
member to project according to the wear on said brake lining, and
which automatically adjusts the space between said brake lining and
said brake member when the brake is not activated so as to become a
predetermined, prescribed magnitude; said detection apparatus
comprising: rotation detecting means for detecting the state of
rotation of said transmission member or of a rotating member which
rotates said transmission member; means for storing a number of
rotations that counts and stores the number of rotations of said
transmission member or said rotating member from said state of
rotation detected by said rotation detecting means; and warning
means for performing a warning operation when it is determined that
the number of rotations stored in said means for storing a number
of rotations has exceeded a predetermined and stored limit number
of rotations.
2. The brake lining wear detection apparatus, according to claim 1,
wherein said friction brake is constituted of a drum brake
comprising: a brake shoes on which the brake lining is provided; a
brake drum that is braked by the brake lining being pressed thereon
when the brake is activated; a pressing screw for pressing the
brake lining against said brake drum when the brake is activated; a
pressing force generating mechanism for applying pressing force to
said pressing screw; a sleeve that screws onto said pressing screw
and is disposed rotatably about the screw shaft for transmitting
the pressing force in the direction of the screw shaft to said
pressing screw; and an adjustment mechanism which rotates said
transmission member about said screw axis to cause the pressing
member to project according to the wear on said brake lining, and
which automatically adjusts the space between said brake lining and
said brake member when the brake is not activated.
3. The brake lining wear detection apparatus, according to claim 1,
wherein said friction brake is constituted of a disc brake
comprising: inner pads and outer pads on which the brake lining is
provided; a rotor that is braked by the brake lining being pressed
thereon when the brake is activated; a pressing screw for pressing
the brake lining against the rotor when the brake is activated; a
pressing force generating mechanism for applying pressing force to
said pressing screw; a sleeve that screws onto said pressing screw
and is disposed rotatably about the screw shaft for transmitting
the pressing force in the direction of the screw shaft to said
pressing screw; and an adjustment mechanism which rotates said
transmission member about said screw axis to cause the pressing
member to project according to the wear on said brake lining, and
which automatically adjusts the space between said brake lining and
said brake member when the brake is not activated.
4. The brake lining wear detection apparatus, according to claim 1,
in which the outer surface of said transmission member or said
rotating member includes a depression or projection that is
displaced when said transmission member or said rotating member is
caused to rotate; and said rotation detecting means comprises: a
shifting member that is in contact with said outer surface and is
displaced along with said depression or projection; and optical
detection means for optically detecting the displacement of said
shifting member; wherein the state of rotation of said transmission
member or said rotating member is detected by counting the number
of passes of said depression or projection by means of said optical
detecting means.
5. The brake lining wear detection apparatus, according to claim 4,
wherein an optically reflective surface is formed on the back end
face of said shifting member; and said optical detection means
comprises a light radiating device for radiating detection light
onto said optically reflective surface; and a light detector for
detecting said detection light reflected from said optically; and
wherein the state of rotation of said transmission member or said
rotating member is detected by detecting change of said detection
light that is detected by said light detector according to the
displacement of said shifting member.
6. The brake lining wear detection apparatus, according to claim 1,
wherein, when it is determined that the number of rotations
calculated and stored by said means for storing a number of
rotations has exceeded a predetermined and stored limit number of
rotations, said warning means activates a warning operation to warn
the driver that said brake lining is approaching the wear limit, by
lighting a brake lining wear warning lamp that is disposed at the
vehicle driver's seat, or by means of a voice alarm or the
like.
7. The brake lining wear detection apparatus, according to claim 1,
wherein said warning means displays a wear notice when the number
of rotations calculated and stored by said means for storing a
number of rotations has exceeded a first stage limit number;
displays a wear warning when has exceeded a second stage limit
number that is greater than the first one; and activates a warning
operation when has exceeded a third stage limit number of rotations
that is still greater than the second one.
8. The brake lining wear detection apparatus, according to claim 7,
wherein said warning operation comprises sounding a warning buzzer
or cutting fuel so that the vehicle speed does not exceed a certain
speed.
9. The brake lining wear detection apparatus, according to claim 1,
wherein the number of rotations stored in the means for storing a
number of rotations is reset to an initial value when said brake
lining member is replaced.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a brake lining wear
detection apparatus for friction brakes, such as drum brakes or
disc brakes, for detecting when the brake lining is abraded to or
beyond a prescribed quantity, for example, up to a wear limit
value.
BACKGROUND OF THE INVENTION
[0002] Friction brakes, such as drum brakes or disc brakes, press a
brake lining (brake pads in disc brakes; in the present
specification, the brake lining is a friction braking member such
as a brake pad) against a brake member such as a rotating brake
drum or disc (rotor), and thereby impart a friction braking action
to the brake drum. The brake lining is gradually worn away by this
friction braking action and when use of the brakes continues beyond
this wear limit, effective braking becomes more difficult. For this
reason, various brake lining wear detection apparatuses, for
detecting when the wear on the brake lining progresses to a certain
wear limit and providing a warning to the driver, are proposed.
[0003] One such apparatus is an apparatus that directly detects
wear on the brake lining. An example of such an apparatus can be
illustrated with the apparatus disclosed by this applicant in the
specification for Japanese Patent Application Laid-open No.
H10-184748. In this apparatus, a detecting jig is disposed from the
back surface of the brake lining and faces the brake drum. Metal
wiring connected to a warning circuit is embedded in the end of
thereof in the form of a loop. The detecting jig is disposed so
that the end portion contacts the brake drum when the wear on the
brake lining progresses to the wear limit. When the end of the
detecting jig is worn or broken by this contact and the metal
wiring therein is cut, the warning circuit detects the breakage of
the circuit from the change in current or voltage and warns the
driver that the brake lining has reached the wear limit.
[0004] Other apparatuses indirectly detect the wear on the brake
lining. For example, the apparatus disclosed in Japanese Patent
Application Laid-open No. H11-351296 detects wear of the brake
lining in drum brakes from the amount of piston movement in a wheel
cylinder causing the swinging of the brake shoe. In drum brakes
comprising an automatic adjusting mechanism, the end position of
piston movement gradually moves as the brake lining wears away. By
having a rod which moves in conjunction with the piston in the
wheel cylinder and monitoring the amount of movement of this rod
with a limit switch, [this apparatus] detects when the brake lining
has reached the wear limit and then warns the driver.
[0005] However, in these types of conventional apparatuses, an
electrical circuit that detects wear of the brake lining and
transmits a signal is disposed near the wheels, which generate
intense vibrations and heat as the vehicle travels. Breakage or
disconnection of the electrical wiring or limit switch therefore
occurs easily. These must therefore be made vibration resistant and
able to tolerate the environment; it therefore becomes difficult to
reduce costs.
[0006] Also, apparatuses that directly detect wear on the brake
lining by the breakage of an electrical circuit have a problem with
false detection because of the breakage of the wiring due to the
vibrations when the vehicle is moving, as discussed above.
Moreover, when the electrical circuit is short circuited, these
apparatuses cannot detect when the brake lining has reached the
wear limit. When wear on the brake lining has been detected and
these detection apparatuses are replaced, the wear detecting jig
must also be replaced with a new part at the same time. For this
reason, parts costs at replacement result in even higher running
costs, and the man hours necessary to connect the electrical wiring
also result in increased running costs. These apparatuses also have
structural problems such as the risk of wiring being cut due to
mistakes during replacement.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a brake
lining wear detection apparatus having high reliability, and that
can be constituted at low cost with a constitution of simple
parts.
[0008] The present invention is an apparatus for detecting wear on
brake linings in a friction brake (for example, drum brake 3 in the
first embodiment or disc brake 5 in the second embodiment)
comprising: a lining member (for example, brake shoe 20 in the
first embodiment or inner pad 120 and outer pad 120' in the second
embodiment) on which the brake lining (lining 23 in the first
embodiment, or pads 123, 123' in the second embodiment) is
provided; a brake member (for example, brake drum 25 in the first
embodiment or rotor 125 in the second embodiment) that is pressed
and braked by the brake lining when the brake is activated; a
pressing member (for example, pressing screw 57, 157 in the first
and second embodiments) for pressing the brake lining onto the
brake member when the brake is activated; means for generating
pressing force (for example, diaphragm, wedge 52, tappet 54 in the
first embodiment, or diaphragm, shaft S, operating shaft 152 in the
second embodiment) for causing the pressing member to exert the
pressing force; a transmission member that screws onto a pressing
member between the pressing member and the means for generating
pressing force and is disposed rotatably about this screw shaft,
and which transmits the pressing force generated by the means for
generating pressing force to the pressing member in the direction
of the screw shaft (for example, sleeves 56, 156 in the first and
second embodiments); and an adjustment mechanism which rotates the
transmission member about the screw shaft to cause the pressing
member to project according to the wear on the brake lining, and
which automatically adjusts the space between the brake lining and
the brake member when the brake is not activated so as to become a
predetermined, prescribed magnitude. Furthermore, the brake lining
wear detection apparatus comprises: rotation detecting means (for
example, displacement detection apparatus 70 in the embodiments)
for detecting the state of rotation of the abovementioned
transmission member or of a rotating member (for example, the wheel
of 168 in the second embodiment) which rotates the transmission
member; means for storing a number of rotations(for example,
controller 30 in the embodiments) that counts and stores the number
of rotations of the transmission member or rotating member from the
state of rotation detected by the rotation detecting means; and
warning means for performing a warning operation when it is
determined that the number of rotations stored in the means for
storing a number of rotations exceeds a predetermined and stored
limit number of rotations.
[0009] As the brake lining (pad) is worn away by the action of the
brakes (friction braking) in friction brakes comprising the
abovementioned adjustment constitution, the pressing member
pressing the lining member is caused to project as the
abovementioned transmission member is caused to rotate about the
screw shaft according to the wear on the brake lining, and the
interval between the brake lining and the brake member when the
brakes are not in use is automatically regulated so as to become a
predetermined, prescribed interval. The number of rotations from
the initial state of the transmission member is equivalent to the
amount of the projection of the pressing member and is an amount
that indicates the amount of wear on the brake lining. The present
invention uses the properties of the regulating action of the
adjustment mechanism and comprises a brake lining wear detection
apparatus [that functions as follows]. The state of rotation of the
transmission member or the rotating member that rotates the
transmission member during the regulating action is detected with
the rotation detecting means. The meansfor storing a number of
rotations calculate and store the number of rotations of the
transmission member or rotating member from the state of rotation
detected. Then, the warning operation means perform a warning
operation when it is determined that the state of rotation stored
in the number of rotations storing means has exceeded a
predetermined and stored limit number of rotations.
[0010] For this reason, the brake lining wear detection apparatus
with the abovementioned constitution makes possible high precision
detection of the state of wear on the brake lining and also does
not require replacement of the wear detecting jig when the brake
lining has worn away and the lining members are replaced.
Consequently, [this apparatus] reduces parts costs as well as the
man hours required for replacement and can therefore keep running
costs low; moreover, [this constitution] makes it possible to
provide a lining wear detection apparatus with which there is no
risk of wiring being cut due to errors made when the lining member
is replaced.
[0011] Moreover, it is preferable that the brake lining wear
detection apparatus be constituted so that the outer surface of the
transmission member or rotating member includes a depression or
projection (flat surface 56c in the first embodiment, or the gear
portion 156a of the wheel 156 in the second embodiment), that is
displaced when the transmission member or rotating member is
rotated; and the rotation detecting means comprise a shifting
member that contacts the outer surface of the rotating member and
is displaced along with the depression or projection, and optical
detecting means (optical detection system as shown in FIGS. 3 and 4
for the embodiments) for optically detecting the displacement of
the shifting member; and so that the state of rotation of the
transmission member or rotating member is detected by counting the
number of passes of the depression or projection detected in this
way.
[0012] Because this is a constitution for optically detecting the
state of rotation of the transmission member or the rotating member
that rotates the transmission member, the wear detection apparatus
with the abovementioned constitution can be constituted so as to be
highly resistant to electrical noise and the like. Also, the
detecting terminal of the optical detecting means and the detection
circuit substrate comprising an LED or photodiode are disposed
separately. Because these can be connected with a flexible optical
fiber with high heat resistance, it is not necessary to include any
electronic components such as electrical wiring or a limit switch
in the vicinity of the wheels, which generate intense vibrations
and heat while the vehicle is moving. Consequently, it becomes
possible to provide a lining wear detection apparatus that is
highly reliable and has high resistance to vibrations and the
environment.
[0013] Furthermore, because the state of rotation of the
transmission member is detected via the shifting member, the
optical detecting means can be optimized to have a small optical
detecting portion. Because the transmission member follows the
movement in the direction of the screw shaft by the braking action
and the rotation about the screw shaft by the adjustment action, it
is necessary to dispose the optical detecting portion over a wide
area when this [movement] is directly detected. Also, lubricant is
necessary in order to ensure the abovementioned movement and powder
from abrasion is also generated by the sliding action over long
periods of time. However, the constitution of the present invention
has the optical detecting portion disposed separately through the
use of the shifting member and therefore the optical detecting
portion can be made small. Moreover, it becomes possible to have a
constitution optimized for optical detection (for example, an
optically reflective surface) wherein the effects of abraded dust
and lubricating oil are eliminated. Consequently, it becomes
possible to provide a lining wear detection apparatus that is
highly reliable and can withstand its environment that is also
small and low-cost.
[0014] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will become more fully understood from
the detailed description given herein below and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention and wherein:
[0016] FIG. 1 is a cross sectional view showing the expander (wheel
cylinder) in a drum brake that is provided the brake lining wear
detection apparatus relating to the present invention;
[0017] FIG. 2 shows two views of the sleeve in the abovementioned
expander;
[0018] FIG. 3 is a drawing to explain the constitution of the
displacement detection apparatus in the brake lining wear detection
apparatus relating to the present invention;
[0019] FIG. 4 is a cross sectional view of the detection heads in
the abovementioned displacement detection apparatus;
[0020] FIG. 5 is a drawing to explain the principle by which
displacement is detected with the abovementioned displacement
detection apparatus;
[0021] FIG. 6 is a block diagram showing the constitution of the
brake wear detection apparatus relating to the present
invention;
[0022] FIG. 7 is a front view showing the constitution of a drum
brake that is provided the abovementioned brake lining wear
detection apparatus;
[0023] FIG. 8 is a sectional side view showing the constitution of
a disc brake that is provided the brake lining wear detection
apparatus relating to the present invention;
[0024] FIG. 9 is a sectional top view from above showing the
constitution of the abovementioned disc brake (cross section at
IX-IX in FIG. 8);
[0025] FIG. 10 is a partial cross sectional view of the adjustment
mechanism portion in the abovementioned disc brake (cross section
at X-X in FIG. 9); and
[0026] FIG. 11 is a partial cross sectional view of the
abovementioned disc brake (cross section at XI-XI in FIG. 9).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] The preferred embodiments of the brake lining wear detection
apparatus relating to the present invention are explained below
with reference to the drawings.
First Embodiment
[0028] FIG. 7 shows an embodiment of the brake lining wear
detection apparatus relating to the present invention applied to a
drum brake; this is explained below with reference to FIG. 7. The
drum brake 3 is affixed to an axle housing (not shown) and
comprises an anchor bracket 7 supporting the brake shoe unit 6, and
a brake drum unit 8 covering the brake shoe unit 6 and that is
disposed rotatably with respect to the anchor bracket 7. This is a
so-called wedge brake using an expander (also called an actuator or
wheel cylinder) 50 having a wedge that presses the brake shoe 20 of
the brake shoe unit 6 on the brake drum 25 of the brake drum 8.
[0029] The brake shoe unit 6 comprises a pair of front and back
supporting arms 21, 21 and brake shoes 20, 20 mounted on these
supporting arms 21, 21; the base portion pivots on an anchor pin 29
inserted in the pin insertion hole 21a of the supporting arm 21 and
is mounted swingably to the left and right in the drawing. The
brake shoe 20 is a member corresponding to the lining members in
the claims and comprises a supporting plate 22 of steel plate and a
brake lining (hereinafter "lining") 23 attached with rivets to this
supporting plate 22. Tension springs 27 connecting [the brake
shoes] together are disposed on the end portions of the brake shoes
20, 20. Usually (brakes released), these brake shoes 20, 20 are
held in a position swung inwards as impelled by the tension springs
27 (position separated from the brake drum 25).
[0030] An expander 50 attached to the axle housing is disposed
between the end portions of the brake shoes 20, 20. As explained in
detail below, the expander 50 causes the pressing screws 57, 57 to
extend outwards to left and right when the brakes are operated.
[The expander] resists the force of the tension springs 27, presses
the end portions of the brake shoes 20, 20, and swings [the brake
shoes] on the anchor pins 29, 29 so that [the brake shoes] are
extended outwards.
[0031] A brake drum 25 (this corresponds to the brake member in the
claims) is disposed outside of the brake shoes 20, 20 so as to
surround the outside of the lining 23, 23. Due to the extending
action of the abovementioned expander, the lining 23, 23 is pressed
to the inner surface of the brake drum 25 opposite thereto and the
rotation of the brake drum 25 is braked by the frictional force
between these. The braking action of the wheel (not shown) on which
the brake drum 25 is mounted is performed thereby. Moreover, as
clear from the above explanation, this drum brake is constituted so
that the leading side and trailing side are bilaterally
symmetrical; this explanation uses the same numbers for the
symmetric components.
[0032] FIG. 1 shows a cross sectional view at line I-I in FIG. 7.
As shown here, the expander 50 comprises a housing 51; a wedge 52
mounted insertably on the housing 51 by the action of the diaphragm
of a chamber (not shown); a roller 53 mounted by means of a
retention plate on this wedge 52; a sleeve assembly disposed
slidably in the direction of the cylinder axis (to the left and
right in this drawing) inserted in a cylindrical cylinder portion
51a formed in the housing 51 and a pressing screw 57 for screwing
onto the sleeve assembly and transmitting the pressing force to the
brake shoe 20 (the combination of these is called the extending
piston); and a boot 59 for preventing the influx of dust to the
sliding portion. Moreover, the right half in FIG. 1 shows the state
of the expander 50 when the brakes are in use and the left half
shows the state of the expander 50 when the brakes are not in
use.
[0033] The sleeve assembly comprises: a tappet 54 having an angled
surface 54a that is pressed to the right and left in the drawing by
the roller 53 by the insertion of the wedge 52; a cylindrical
sleeve 56 that is connected to the tappet 54 by a snap ring 55 and
that is able to move relatively [to the tappet] in a rotary
direction about the cylinder shaft; and a wrap spring 61, the outer
surface of one end of which is anchored to the cylindrical inner
surface of the tappet 54 and the outer surface of the other end of
which is anchored to the cylindrical inner surface of the sleeve
56. The wrap spring 61 has the function of a one way clutch; in the
present embodiment, [the wrap spring] allows relative rotation in
the direction of decreasing coil outer diameter (rightwards
rotation in the case of a right-wrapped spring, for example). In
the direction of increasing coil outer diameter (leftwards rotation
in this case), the outer diameter of the spring clings to the
tappet 54 and the sleeve 56 and joins with these to prevent
relative rotation.
[0034] The pressing screw 57 comprises a female screw 56a formed on
the cylindrical inner surface of the sleeve 56 and a male screw
portion 57a that screws into 56a. [The pressing screw] is provided
a regulating dial portion 57b extending outside of the housing 51
and has a form of a rod. A clip 58 is mounted on the regulating
dial portion 57b; [the clip] engages with the brake screw 20 while
being engaged rotatably about the screw shaft of the pressing screw
57.
[0035] A helical spline 56b is formed about the outer peripheral
portion of the housing in the sleeve 56, as shown in the exterior
view (two views) of the sleeve 56 in FIG. 2a and b. A drive ring 62
is screwed onto this helical spline 56b with a prescribed looseness
(3 mm, for example) in the direction of the cylinder axis. The
drive ring 62 has a conical surface 62a that is in contact with the
tapered surface 51b formed on the end surface of the cylinder
portion of the housing 51. [The drive ring] is formed so that a
constant frictional force is developed between these contact
surfaces by the spring 63 that impels the drive ring 62 towards the
interior of the housing.
[0036] Part of the cylindrical surface is chamfered and the flat
surface 56c is formed on the outer surface towards the inside of
the housing in the sleeve 56. On the housing 51, the detecting
heads 80, 80 of the displacement detection apparatus 70 are mounted
at positions corresponding to the outer surface of this chamfered
sleeve (positioned in the direction of the cylinder axis).
[0037] FIG. 3 shows the principal constitution of the displacement
detection apparatus 70. As shown here, [the apparatus 70]
comprises: a projecting LED 71, a feedback optic fiber 72 for
detecting the emission state of the LED 71, a feedback photodiode
73, radiated light optic fibers 74L and 74T for guiding light from
the LED 71 to the leading detecting head 80L and the trailing
detecting head 80T, reflected light optic fibers 75L and 75T for
guiding reflected light from the detecting heads 80L, 80T, leading
photodiode 76L and trailing photodiode 76T for detecting the
respective reflected light, and flexible metal tubes 78L and 78T
for protecting the radiated light optic fibers 74L, 74T and
reflected light optic fibers 75L and 75T. This is an apparatus for
detecting the displacement position of the detected portion in the
detecting head portion by guiding light from the LED 71 to the
detecting head with the radiated light optic fiber and detecting
the quantity of light reflected from this detecting head with a
photodiode through a reflected light optic fiber. Moreover, the
leading and trailing sides of the displacement detection apparatus
70 have the same constitution and therefore the same numbers are
used in the following explanation with the letters L and T
omitted.
[0038] FIG. 4 shows the constitution of the detecting head portion
in detail. As shown in this figure, the detecting head 80 comprises
a body 81, a shifting member 82, a spring 83, a fiber end member
84, and O-rings 87, 88.
[0039] The body 81 has O-ring grooves in the outer surface and one
end surface that faces the inside of the housing 51 in the mounted
position (this is the left side in the figure and is hereinafter
called the front end); a bearing hole 81a is formed in the central
axis portion. The shifting member 82 comprises a shaft portion 82b
supported slidably by the body 81 and a flange portion 82c that
spreads in the form of a lip. In the mounted position, a shaft
portion 82b is inserted into the body from the back end that is the
outside of the housing 51 and is mounted with the outer surface of
the flange portion 82c impelled by a pressing spring 83 towards the
front end. The back end surface of the flange portion 82c is ground
flat and an optically reflective surface 82d is formed.
[0040] The fiber end member 84 supporting the other end of the
spring 83 attaches and supports the radiated light optic fiber 74
and the reflected light optic fiber 75, while holding [the fibers]
at a prescribed distance from the central shaft in the front end
portion and exposing the end surfaces of both fibers; [the fiber
end member] is affixed to the body 81 with a known attachment
method such as press fitting or caulking of the outer surface of
the member.
[0041] In the interior space thus formed within the body 81, the
fiber end surfaces of the radiated light optic fiber 74 and the
reflected light optic fiber 75 are disposed opposite to the
optically reflective surface 82d of the shifting member 82. With
the shifting member 82 continually impelled towards the front end
by the spring 83, the shaft is sealed by the O-ring 87 in the front
end portion. The lubricating oil and dust from the housing 51 are
thereby prevented from penetrating to the optically reflective
surface 82d.
[0042] FIGS. 5a and b model the change in the state of reflection
of light within the body 81 when the relative interval between [the
reflective surface and the ends of the optic fibers] is changed in
the case where the shifting member 82 moves in the direction of the
axis, meaning that the optically reflective surface 82d is
displaced with respect to the end surfaces of the radiated light
optic fiber 74 and the reflected light optic fiber 75, in the
detecting head 80 portion with the constitution as described above.
The principle of detection by the displacement detection apparatus
70 is explained below using these drawings.
[0043] The condition shown in FIG. 5a shows the state wherein light
strikes and is reflected by the optically reflective surface 82d
when the shifting member 82 is extended by the force of the spring
83 to the flat surface 56c of the sleeve 56. In this state, the
incident light Li from the radiated light optic fiber 74 is
reflected by the optically reflective surface 82d. The reflected
light Lr strikes the reflected light optic fiber 75 and is detected
as a high brightness state (High) by the leading or trailing
photodiode 76 in FIG. 3.
[0044] The condition shown in FIG. 5b shows the state wherein light
strikes and is reflected by the optically reflective surface 82d
when the shifting member 82 is pressed by the cylindrical surface
of the sleeve 56 against the force of the spring 83 and is slid
towards the inside of the body 81. In this state, the incident
light Li from the radiated light optic fiber 74 is reflected from a
position on the optically reflective surface 82d that is different
from the position in the figure a above. Most of the reflected
light Lr does not strike the reflected light optic fiber 75. For
this reason, [this state] is detected as a low brightness state
(Low) by the leading or trailing photodiode 76 in FIG. 3.
[0045] The leading or trailing photodiode 76 detects the intensity
of the reflected light observed through the reflected light optic
fiber 75. Consequently, as clear from such a principle for
detection, it is possible with this displacement detection
apparatus 70 to make an analog calculation of the displaced
position of the shifting member 82 from the intensity of the
reflected light detected by the photodiode 76.
[0046] In order to simplify the constitution in the present
embodiment, the constitution used for the displacement detection
apparatus 70 is able to distinguish between two states, whether the
amount of the reflected light is in a high brightness state (High)
or a low brightness state (Low), meaning that the position at which
the shifting member 82 is in contact with the outer surface of the
sleeve 56 is either the chamfered flat surface 56c (High) or the
cylindrical surface (Low). Moreover, the example above shows that
the quantity of reflected light is in a low brightness state when
the shifting member 82 is tracing the over the cylindrical surface,
but is also possible to have the opposite be the case.
[0047] The feedback photodiode 73 in FIG. 3 detects the intensity
of light emitted from the projecting LED 71 and is disposed in
order to reduce the level of error when calculating the
displacement position (brightness determination) from the intensity
of the reflected light. Consequently, there is no concern of false
detection when the intensity of light emitted from the LED 71
changes over time or when the LED 71 is not emitting.
[0048] Next are explained the action of the expander 50 in the case
of braking with the drum brakes 3, having the constitution
discussed above, and the action of the adjustment mechanism when
the lining wears away. As discussed above, when the brakes are
operated, the wedge 52 of the expander 50 is pressed downwards in
FIG. 1 by the action of a diaphragm, not shown. This pressing force
is changed to a sideways pressing force through the rollers 53 by
the action of the inclined surface of the wedge 52 and tappet 54
and is transmitted to the sleeves 56. The sleeves 56 on either side
receive this pressing force and are extended (expanded) to both
sides along the cylinder shaft so as to expand from the center of
the expander (this is the position in the right half of FIG.
1).
[0049] The helical spline 56b formed on the outer surface of the
sleeve 56 and the screw tooth surface of the drive ring 62 that
engages therewith are formed so as to have a prescribed looseness
(3 mm, for example) in the direction of the cylinder axis as
discussed above. When the range of movement of the sleeve 56 is
within the range of this looseness due to the abovementioned
braking action, the sleeve 56 advances within the cylinder 51a
without causing rotation of the drive ring 62.
[0050] The pressing screw 57, screwed onto the sleeve 56, engages
with the brake shoe 20 through the clip 58 that holds the
adjustment dial 57b. [The pressing screw] advances along with the
sleeve 56 without rotating due to the frictional resistance of this
clip 58 and the frictional resistance at the screw surface. [The
pressing screw] then presses both the left and right brake shoes
20, causing the lining 23 to be pressed against the brake drum 25
by swinging these about the anchor pins 29, and brakes the rotation
of the brake drum 25 by the frictional force between these
members.
[0051] When the braking action is released, the wedge 52 moves
upwards in FIG. 1 and the pressing screw 57 and sleeve assembly
retract towards the center of the housing 51 (this is the state in
the right half of FIG. 1) due to the action of the tension spring
27 extending between the brake shoes 20, 20. At this time, because
the range of movement of the sleeve 56 is within the abovementioned
range of looseness, the sleeve 56 moves within the cylinder 51a
without rotating, as during the extending movement.
[0052] As the lining 23 wears away, the amount of movement of the
pressing screw 57 and sleeve assembly in order to attain the same
braking effect when the brakes are applied becomes large. At this
time, the range of movement of the sleeve 56 when the brakes are
applied exceeds the range of looseness with the screw tooth surface
of the drive ring 62. The drive ring 62 screws onto and contacts
the tooth surface 56b of the moving sleeve 56 and receives pressing
force towards the outside of the housing 51. At this time, due to
the force from the drive spring 63, the frictional force of the
conical surface 62a that is pressed by the tapered surface 51b of
the housing 51 is lessened and the drive ring 62 rotates along the
tooth surface of the spline 56b. Moreover, at this time the sleeve
56 and pressing screw 57 advance without rotating due to the
one-way function of the wrap spring 61.
[0053] When the braking action is released and the sleeve 56
returns into the housing 51, the drive ring 62, having been
released from contact with the screw surface, is pressed towards
the inside of the housing by the force of the drive spring 63. The
conical surface 62a contacts the tapered surface 51b of the housing
51 and acts as a wedge. Consequently, the rotation of the drive
ring 62 is suppressed by the frictional resistance at the context
surface. Because of the looseness between the helical spline and
the drive ring 62, the sleeve 56 contracts without further action
and without resistance, but during extension, the working length
corresponding to the extension from the rotation of the drive ring
62 again contacts the contraction side screw surface of the drive
ring 62 during contraction.
[0054] At this time, rotation of the drive ring 62 is suppressed as
discussed above and [the drive ring] cannot rotate freely. On the
other hand, the wrap spring 61 contained within the sleeve assembly
has a one-way function. In the case where [the wrap spring]
contacts the elongation side screw surface so that the sleeve 56
presses the drive ring 62, the wrap spring 61 limits rotation in
the direction along this screw surface (leftwards rotation, for
example) and causes the drive ring 62 to rotate, but oppositely
allows rotation in the direction of the sleeve 56 that is rotated
along the contracted side screw surface (rightwards rotation, for
example). In the contracted end portion, then, the sleeve 56 is
rotated along the tooth surface of the drive ring 62.
[0055] As discussed above, the pressing screw 57 is engaged with
the brake shoe 20 and receives frictional resistance from the clip
58 that is prevented from rotating about the axis. This frictional
resistance is greater than the frictional resistance of the engaged
screw surface, and the pressing screw itself therefore does not
rotate along with [the clip]. For this reason, the sleeve 56
rotates independently with respect to the tappet 54 and the
pressing screw 57. The engaged pressing screw 57 is payed out
according to the angle of rotation by this rotation of the sleeve
56.
[0056] When the lining 23 wears away, the adjustment mechanism in
this drum brake 3 causes the sleeve 56 to rotate according to the
stroke of the sleeve 56 when the brakes are applied and
automatically adjusts by paying out the engaged pressing screw 57,
so that the space between the lining 23 and the brake drum 25
remains constant. The amount by which the pressing screw 57 is
payed out equals the amount of wear on the lining 23; this quantity
and the number of rotations of the sleeve 56 are made equal by
converting the pitch of the engaged screw.
[0057] For example, the amount of the lining 23 used up to the wear
limit is 10 mm and the amount of the pressing screw 57 let out
corresponding to this amount of wear is 20 mm. When the screw pitch
of the pressing screw 57 and sleeve 56 is 1 mm, then the wear limit
position has been reached when the sleeve 56 has turned 20 times.
Consequently, as discussed above, it is possible to detect the
state of wear of the lining 23 at the current time by detecting the
flat portion 56c formed on the outer surface of the sleeve 56 using
the displacement detecting device 70 and counting up the number of
times that this flat portion has passed, meaning the number of
rotations.
[0058] FIG. 6 is a block diagram of the constitution of the lining
wear detection apparatus 1 and is explained below. This apparatus
comprises the displacement detecting device 70 discussed above, a
controller 30, a warning apparatus 90, and a reset switch 35. [The
information as to] whether the intensity of the reflected light is
bright (High)=1 or is not bright (Low)=0, indicating whether the
rotary position of the sleeve 56 is at the flat surface 56c or the
cylindrical surface, is input to the controller 30 from the
displacement detecting device 70 as a binary signal of 1 or 0. When
the value of the signal changes from 0 to 1 (or from 1 to 0), the
controller 30 adds 1 to the cumulative number of rotations already
stored in the prescribed memory in the controller.
[0059] The controller 30 compares the cumulative number of
rotations of the sleeve 56 to a predetermined and stored number of
rotations for a wear warning (called the limit number of rotations
in the claims; for example, this can be 19 rotations (=9.5 mm of
wear) in the example discussed above). When [the controller]
determines that [the number of rotations] has not reached the
number of rotations for a wear warning, [the controller] continues
to count without generating a warning command. When [the
controller] determines than the number of rotations for a wear
warning has been reached and exceeded, [the controller] outputs a
warning command signal to the warning device 90.
[0060] The warning device 90 performs a warning action based on the
warning command signal from the controller 30. For example, [the
warning device] informs [the driver] that the lining 23 is
approaching the wear limit by lighting a brake lining wear warning
lamp that is disposed at the vehicle driver's seat or by a voice
alarm. It is also possible for the controller 30 and warning device
90 to have a plurality of warning levels. For example, when the
number of rotations of the sleeve 56 has exceeded the first level,
a wear notice display is made. Then as the wear progresses, a wear
warning display is made at the second stage. At the third stage, a
warning buzzer is activated and a warning operation, such as
cutting fuel so that the vehicle speed cannot exceed a certain
level, is performed.
[0061] When warning operations are made in this way, a person
performs the operation to replace the worn brake shoes 20 based on
these warnings, because the lining 23 is approaching the wear limit
state and further use will result in reduced braking power. After
the brake shoes are replaced, the reset switch 35 in the wear
detection apparatus is operated and the cumulative number of
rotations stored in the internal memory is reset to 0. Moreover,
the reset switch 35 may also be automatically be set by the
operation of replacing the brake shoes 20 and without a manual
operation. For example, for brakes of the type where the anchor pin
29 is removed when the brake shoes 20 are replaced, the operation
to replace the brake shoes 20 can be detected by detecting the
engagement of the anchor pin 29 electrically or mechanically.
Consequently, the reset switch 35 can have a constitution such that
the cumulative number of rotations stored in the internal memory is
reset to 0 based on such a detection signal.
[0062] Consequently, with the constitution as explained above, only
the brake shoes 20 need to be replaced and it is not necessary to
replace the wear detecting jig or the like at the same time when
the lining 23 wears away and the brake shoes 20 are replaced. For
this reason, it becomes possible to provide a wear detection
apparatus with reduced parts costs and replacement time and that
can keep running costs low. Additionally, there is no risk of
wiring being cut in error when the brake shoes are replaced. Also,
because this constitution allows optical detection of the number of
rotations of the sleeve equal to the amount of wear of the lining
23, it becomes possible to constitute a wear detection apparatus
that is highly resistant to noise such as electrical noise.
Furthermore, because the detecting head 80 of the displacement
detection apparatus 70 is disposed separately from the detection
circuit substrate comprising an LED 71 and photodiode 76, it is not
necessary to dispose electronics components in the vicinity of the
wheels which generate intense vibrations and heat while the vehicle
is moving. Consequently, it becomes possible to provide a lining
wear detection apparatus that is highly reliable and highly
resistant to vibrations and its environment.
[0063] Also, the displacement detection apparatus 70 detects the
state of rotation of the sleeve 56 in a detection head 80 through a
shifting member 82. As a result, the reflective surface 82d
(optical detecting portion) can be made small in size, and moreover
it becomes possible to easily constitute an optically reflective
surface which is optimal for optical detection and is unaffected by
abraded dust and the lubricating oil that is necessary to sustain
stable action of the sleeve. Consequently, it becomes possible to
provide a small and low-cost lining wear detection apparatus that
is highly reliable and can withstand its environment.
[0064] In the abovementioned embodiment, a flat surface 56a for the
detection of the state of rotation is formed at one location on the
sleeve 56 and one signal per rotation of the sleeve 56 is counted
in this example. However, it is also possible to have a plurality
of such flat surfaces. For example, if flat surfaces are formed at
four locations on the outer surface of the sleeve, the number of
signals per rotation of the sleeve increases to four and the 20
rotations of the sleeve that are the wear limit in the example
discussed above correspond to a total of 80 signals. The amount of
wear on the lining per signal then becomes 0.125 mm. Consequently,
increasing the number of detected locations can increase the
resolution of the amount of wear on the lining.
[0065] Change in the binary signal input to the controller 30 from
the displacement detection apparatus 70 is preferably determined by
performing equalization processes for the signal value within a
prescribed period of time or determining that the signal value has
changed from 0 to 1 when the bright signal=1 is detected after a
certain period of time. In the case where the action of an
apparatus using this wear detection apparatus is stopped, such as
when the main ignition switch of the vehicle is turned off, the
controller 30 stores the signal state from directly before that
stoppage and uses this in continuing to make the determination when
the vehicle is restarted. With such a constitution, it becomes
possible to improve the precision of detection by the lining wear
detection apparatus while preventing incorrect addition by the
controller 30.
[0066] Also, it is preferable that the displacement detection
apparatus 70 output an error when there is some anomaly within the
displacement detection apparatus such as when the LED 71 is cut
off, and that the controller 30 make a display to that effect on
the warning display device 90 based on this error input. With such
a constitution, it becomes possible to provide a lining wear
detection apparatus that is highly reliable and prevents a
situation wherein a warning display is not made although the lining
has really worn away.
Second Embodiment
[0067] Next, another embodiment of the lining wear detection
apparatus relating to the present invention is explained. In this
embodiment, the same type of wear detection apparatus as above is
applied to disc brakes. Like the embodiment discussed above, this
apparatus is an adjustment mechanism for automatically regulating
the space between the pads and rotors when the pads (lining) are
worn away, wherein the state of rotation of a sleeve that turns
with the adjustment operation is detected by detecting the state of
rotation of the wheel causing this sleeve to rotate and a warning
operation is performed according to the number of rotations. This
apparatus is explained below with reference to the drawings.
[0068] FIG. 8 shows a cross sectional view from the side of the
disc brake 5. As shown in FIG. 9, a cross sectional view taken at
IX-IX in FIG. 8, [the disc brake] comprises a caliper unit 105
mounted on the axle housing, not shown, and a rotor unit 108
mounted to rotate with the wheel. The caliper unit 105 comprises: a
shaft S that is extended by a supply of compressed air to a chamber
C when the brakes are operated; an operating shaft 152 that is
mounted swingably on housing 151 and swings with the extension and
retraction of the shaft S; a disc-shaped tappet 154 that is offset
from the swing axis of this shaft [152] and receives a pressing
force from contact of the operating shaft 152 with the rollers 153,
153 mounted parallel thereto; a disc-shaped sleeve 156 (also called
a nut) that is supported by the housing so as to swing in the
direction of the axis of the pressing operation and to rotate about
this axis; a pressing screw 157 (also called a tappet) that screws
onto and is supported by a screw 156a formed on the inner
cylindrical surface of the sleeve 156 and transmits the pressing
force to the pad 120; and an inner tappet 120 that is attached to
the pressing screw 157 by a locking plate 158 and an outer tappet
120' that is connected to the housing 151 by a connecting member
129. The rotor 125 of the rotor unit 108 is disposed between both
pads at a constant distance when the brakes are not in use.
[0069] When the brakes are operated, the shaft S that is anchored
to a diaphragm mounted within the chamber elongates due to a supply
of compressed air to the chamber C, presses the operating shaft
152, and is caused to swing as shown by the double dotted line in
FIG. 8. At this time, because the roller 153 is mounted offset from
the swinging axis of the operating shaft 152, the swinging movement
of the operating shaft 152 is converted to a movement, in the
direction of the axis of the pressing action of the sleeve 156,
through the roller 153. With the pressing force converted in this
way, the pressing screw 157 that is screwed onto the sleeve 156
presses the inner pad 120 and presses the pad 123 to the rotor 125.
At this time, the housing 151 receives the reaction force and moves
to the left in FIG. 8, pulling the outer pad 120' through the
connecting member 129 and pressing the pad 123' to the rotor 125.
Therefore, when the pressing screw 157 is pressed from one side,
the rotor 125 is pressed between the inner pad 120 and the outer
pad 120'; [the rotor] is pressed with the same pressure by both
pads, resulting in friction braking of the turning rotor.
[0070] As shown in a cross sectional view in FIG. 9, the adjustment
mechanism in this disc brake 5 comprises an adjustment assembly 160
that extends parallel to the axis of the swinging and turning (axis
of pressing operation) of the sleeve 156. This assembly 160
comprises an adjustment wheel 163, a pin 161, a spring 164, a wrap
spring 165, a drive ring 166, a multiple disc clutch 167, a wheel
168, and a gear wheel 169 centered about a bolt 162 as a central
shaft supporting each member.
[0071] One end of the pin 161 is anchored to the abovementioned
operating shaft 152 and converts the swinging movement of this
shaft to a rotary movement of the adjustment wheel 163. The wrap
spring 165 is wound around the adjustment wheel 163 and the drive
ring 166. In the case of rotation in the direction in which the
sleeve 156 is projected due to the operation of the brakes (in this
embodiment, this is when the coil is decreasing), [the wrap spring]
wraps around the adjustment wheel 163 and drive ring 166 and causes
them to rotate together. In the case of rotation the opposite
direction (when the coil is increasing), [the wrap spring] causes
these to be engaged within the range of a weak frictional force and
allows relative rotation with a rotary force in excess of [the
frictional force].
[0072] FIG. 10 shows a cross sectional view taken at X-X in FIG. 9
of the cylindrical drive ring 166 and the multi-plate clutch 167.
As shown in this figure, [the drive ring 166 and the multi-plate
clutch 167] are engaged with each other through the tag T of the
multi-plate clutch and the gap (looseness) G in a prescribed
direction of rotation at a cutout portion 166 formed in the outer
portion of the drive ring 166. Rotary force is not transmitted to
the multi-plate clutch 167 in the case where the angle of rotation
of the drive ring 166 is within the range of the gap G. The
multi-plate clutch 167 comprises a tag clutch plate 167a having a
tag projecting into the cutout portion of the drive ring and
engaging with the drive ring 166; and a wheel clutch plate 167b
that does not have a tag and is engaged and rotates with the wheel
168. [The plates in the multi-plate clutch] are pressed in the
direction of the shaft by the spring 164 and are engaged by
friction with each other.
[0073] The wheel 168 is supported rotatably by the bolt 162 and
also engages with each gear portion 156b formed on the outside of
the sleeve 156 through the gear 168a that is disposed on the
exterior portion of the wheel. Also, the left and right sleeves
156, 156 are connected and engaged by the gear portions 156b, 156b
with a gear wheel 169 that is supported in the center thereof. The
rotation of the wheel 168 is transmitted to both the left and right
sleeves 156 by these gear trains.
[0074] In an adjustment mechanism with the constitution described
above, the adjustment wheel 163 is rotated in accord with the angle
of the swinging operation of the operating shaft 152 when the
brakes are applied. The rotation of the adjustment wheel 163 is
transmitted to the wrap spring 165; according to the direction of
this rotation (direction of brake operation), the wrap spring 165
connects and causes the rotation of the adjustment wheel 163 and
the drive ring 166, whereupon the rotation of the adjustment wheel
163 is transmitted without further processing to the drive ring
166. The rotation of the drive ring 166 is not transmitted to the
multi-plate clutch 167 until the abovementioned gap G is filled up.
When this gap is filled and is then rotated, that rotary force is
transmitted to the wheel 168 by the multi-plate clutch 167.
[0075] Meanwhile, when the pressing screw 157 is pressed by the
swinging action of the operating shaft 152 and the inner pad 120 is
pressed to the rotor 125, a frictional force is developed at the
screw surface between the pressing screw 157 and the sleeve 156. As
a result of the development of this frictional force, the rotary
force of the abovementioned wheel 168 is suppressed by the gear
portion 156b of the engaged sleeve 156. For this reason, when the
drive ring 166 is rotated further after the pad 123 and rotor 125
are in contact, slipping occurs between the tag clutch plate 167a
and the wheel clutch plate 167b of the multi-plate clutch 167 that
is anchored by friction between the drive ring 166 and the wheel
168, and the wheel 168 does not rotate.
[0076] When the brakes are released and the operating shaft 152
starts to return, the adjustment wheel 163 returns around the pin
161 in the opposite direction from when the brakes are applied. The
wrap spring 165 engages the drive ring 166 and the adjustment wheel
163 by a weak frictional force opposing this rotation. The drive
ring 166 is caused to rotate [by an amount of] the gap G between
the tag T of the multi-plate clutch 167 and the cutout portion 166a
of the drive ring 166. Rotation beyond that amount has no effect
and does not cause rotation of the wheel 168. In other words, when
the braking action is ended, the abovementioned gap G remains held
with respect to the direction of rotation of the drive ring during
brake operation.
[0077] Next, when the inner pad and outer pad wear away because of
the braking action, the angle of the swinging operation of the
operating shaft 152 until the pads contact the rotor when the
brakes are operated becomes high. For this reason, in the state
where the drive ring 166 rotates and the gap G is filled with the
tag T of the multi-plate clutch 167, the inner pad 120 is not yet
in contact with the rotor 125 and the sleeve 156 is able to rotate
without receiving the weak frictional resistance from the screw
surface of the pressing screw 157. Consequently, the force of
rotation of the drive ring 166 is transmitted to the left and right
sleeves 156, 156 through the multi-plate clutch 167, the gear 168a
of the wheel 168, and the gear wheel 169, and the sleeve 156
rotates in the direction in which the engaged pressing screw 157
projects.
[0078] After that, when the inner pad 120 and rotor 125 are in
contact and the frictional force acting on the engaged screw
surface increases, the rotation of the sleeve 156 is suppressed.
When the frictional resistance of the screw surface exceeds the
frictional holding force in the multi-plate clutch, the rotation of
the sleeve 156 stops and slipping occurs in the multi-plate clutch.
The action when the brakes are subsequently released is the same as
discussed above.
[0079] In this way, when the inner pad and outer pad become worn,
the adjustment assembly 160 causes the sleeve 156 to rotate and
acts so as to project the pressing screw 157. The number of
rotations of the sleeve 156 is equivalent to the amount of the
pressing screw 157 that is let out, meaning the amount of wear on
the pads, as in the embodiment discussed above. In the present
embodiment, the state of rotation of the sleeve 156 is detected by
detecting the state of rotation of the wheel 168 related by a
certain number of teeth to the rotation of the sleeve 156.
[0080] When using the same type of displacement detecting device as
in the embodiment discussed above in the present embodiment, the
detecting head 80 is mounted so that the axis of rotation of the
wheel (bolt 162) intersects with the axis of displacement of the
shifting member at a position that is the exterior portion of the
wheel 168 in the housing 151. FIG. 11 shows a cross sectional view
at XI-XI in FIG. 9 of the relationship between the wheel 168 and
the detecting head 80. The end portion 82a of the shifting member
82 touches the exterior portion of the geared outside of the wheel
168 and is disposed so as to be able to detect the passage of the
gear teeth due to the rotation of the wheel 168.
[0081] The constitution of the lining wear detection apparatus 1 is
the same as explained using FIG. 6. [The lining wear detection
apparatus] comprises the displacement detection apparatus 70,
controller 30, warning apparatus 90, and reset switch 35. The
controller 30 monitors the state of the zero or one value (binary
signal) input from the displacement detection apparatus 70 and adds
one to the cumulative count value stored already in the prescribed
memory of the controller when the signal value changes from 0 to 1
(or changes from 1 to 0).
[0082] The controller 30 then compares the cumulative tooth count
value of the wheel 168 that is stored with the predetermined and
stored count value for a wear warning (for example, when the wear
limit is 10 mm as in the embodiment discussed above, this is the
tooth count value corresponding to 9.5 mm for a wear warning that
is found from converting the engaged screw pitch of the pressing
screw 157 and sleeve 156 and the gear ratio of the sleeve 156 and
wheel 168), or in other words, the tooth count value corresponding
to the number of rotations of the sleeve for a wear warning. When
[the controller] determines that the wear warning count value has
not been reached, [the controller] continues counting without
generating a warning command; when the [controller] determines that
the wear warning count value has been reached, [the controller]
outputs a warning command signal to the warning device 90. The
warning device 90 performs a warning operation as discussed above
based on the warning command signal from the controller 30.
[0083] Consequently, when the pads 123, 123' wear away and the
inner pad 120 and outer pad 120' are replaced, it is necessary only
to replace these pads 120, 120' and it is not necessary to replace
the wear detecting jig and so forth at the same time. Consequently,
it becomes possible as with the abovementioned embodiment to
provide a wear detection apparatus that can reduce running costs
and at the same time have no risk of wiring being cut in error when
the pads are replaced. Also, because this is a constitution wherein
pad wear is optically detected, it becomes possible to provide a
wear detection apparatus that is highly resistant to noise such as
electrical noise and it is not necessary to dispose electronics
components in the vicinity of wheels which generate intense
vibrations and heat while the vehicle is moving. Consequently, it
is possible to provide a lining wear detection apparatus that is
highly reliable and is able to withstand vibrations and its
environment.
[0084] Also, the displacement detection apparatus 70 detects the
state of rotation of the sleeve 156 through a shifting member 82.
As a result, the reflective surface 82d (optical detecting portion)
can be made small in size, and moreover it becomes possible to
easily constitute an optically reflective surface which is optimal
for optical detection and is unaffected by abraded dust and the
lubricating oil. Consequently, it becomes possible to provide a
small and low-cost lining wear detection apparatus that is highly
reliable and can withstand its environment.
[0085] In the abovementioned embodiment, as means for detecting the
state of rotation of the sleeve 156, a displacement detection
apparatus 70 detects the state of rotation of the gear 168a formed
on the wheel 168 causing rotation of the sleeve 156 at the time of
the adjustment action. However, any means that detect the state of
rotation of the sleeve 156 are acceptable and this constitution is
not limited by the abovementioned embodiment. For example, it is
possible to use and attain the same effects with the following: a
constitution for directly detecting the state of rotation of the
sleeve 156, or a similar constitution for detecting the state of
rotation of the intermediate gear wheel 169.
[0086] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
RELATED APPLICATIONS
[0087] This application claims the priority of Japanese Patent
Application No. 2000-008529 filed on Jan. 18, 2000, which is
incorporated herein by reference.
* * * * *