JPH11351296A - Brake lining wear detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake lining wear detection device capable of reducing the running cost of a drum brake. SOLUTION: A brake lining wear detection device is provided with right and left rods 12, 13 which are locked to rod connection parts 25b, 26b of right and left clips to be mounted on right and left pistons of a wheel cylinder and are expanded along with the expansion/contraction of the pistons. When a brake lining is worn, the expansion of the pistons is increased, and the movement of the rod connection parts 25b, 26b reaches a specified movement, the right and left rods 12, 13 are also moved in the right-to-left direction and a contact ball 18c is depressed by inclined surfaces 12g, 13g of a dog part 12f(13f). A warning switch 18 is operated to light a warning lamp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake lining wear detecting device for detecting when a brake lining has worn out to a predetermined amount or more, for example, to a wear limit in a drum brake mainly used for a vehicle.

[0002]

2. Description of the Related Art In a drum brake, if the brake lining is worn beyond the wear limit, there is a problem that the brake becomes ineffective. For this reason, in a vehicle having a drum brake, a device has been proposed in which when the brake lining has worn down to the wear limit, this is detected and an alarm is issued to a driver. Such an apparatus is disclosed in Japanese Patent Application No. 8-349621.
There is an abrasion detector as disclosed in the specification of Japanese Patent Application Laid-Open No. H10-260,878.

This wear detector detects the wear of a brake lining in a drum brake. A wear detector having a metal wire therein is disposed at a predetermined position. The brake drum comes into contact with the wear detector. When the brake drum comes into contact with the wear detector, the wear detector is cut off at that part and the internal metal wire is cut, and this cut is detected by interrupting the current flowing through the metal wire, It detects the wear of the brake lining.

[0004]

However, in a so-called disconnection type wear detector which detects the wear of the brake lining by cutting such an internal metal wire,
Each time a brake shoe with worn brake linings is replaced, the wear detector must also be replaced, which causes a problem that replacement work is complicated and running costs are increased. In the case of drum brakes, usually 2
Although a plurality of brake shoes are provided, the above-described configuration requires a wear detector to be provided for each brake shoe, and thus has a problem that running costs are further increased.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a brake lining wear detecting device capable of reducing a running cost of a drum brake.

[0006]

In order to achieve the above object, a brake lining wear detecting device of the present invention detects wear of a brake lining in a drum brake, and the drum brake is provided with a brake lining. And a brake drum which is rotatably mounted so as to cover the brake shoe from the outside in the axial direction and to which a brake lining is pressed when the brake is operated. The brake lining wear detecting device includes a wheel cylinder, a moving member (for example, the left and right rods 12, 13 and the left and right clips 25, 26 described in the embodiment), and a detection signal transmitting unit (for example, the warning described in the embodiment). Switch 18)
It is composed of

The wheel cylinder includes a telescopic piston (for example, the left and right pistons 23a, 23
b, 23c, 23d and screw adjuster 23
c, 23d). The piston is extended in a state where the piston is in contact with the brake shoe, so that the brake lining is pressed against the brake drum and the brake is operated. In addition, as a device for pressing the brake lining against the brake drum in this way, there are various configurations such as extending the piston using hydraulic pressure, extending the piston using a wedge-shaped member (wedge), and the like. Devices using hydraulic pressure are often referred to as wheel cylinders, and devices using wedges are sometimes referred to as actuators, but the wheel cylinder in the present invention is not limited to its name. It is a concept including all devices for pressing the brake lining against the brake drum.

The moving member is locked by the piston of the wheel cylinder and moves with the extension operation of the piston. The detection signal transmitting means determines that the brake lining has worn by a predetermined amount when the moving amount of the moving member reaches the predetermined moving amount, and transmits a wear detection signal.

According to the brake lining wear detecting device configured as described above, if the brake lining wears during the operation of the brake, the amount of extension of the piston in the wheel cylinder increases, so that the amount of movement of the moving member also increases. Therefore, if the moving amount of the moving member corresponding to the wear amount of the brake lining is obtained in advance, and if the moving member is set to move by a predetermined moving amount when the brake lining has worn down to the wear limit, the brake can be set. When the lining has worn down to the wear limit, the detection signal transmitting means can transmit a wear detection signal. And
When the brake lining is worn, the moving member and the detection signal transmitting means do not need to be replaced only by replacing the brake shoe, so that the running cost of the drum brake can be reduced.

The brake lining wear detecting device according to the present invention has two brake shoes and, in a drum brake provided with two pistons in a wheel cylinder, moves a moving member to each of the two pistons. It is preferable to provide two movably with extension. Then, a detection signal transmitting means is provided so as to transmit a wear detection signal when a moving amount of any one of the two moving members reaches a predetermined moving amount. With such a configuration, the wear of the brake linings of the two brake shoes can be detected by one detection signal transmission unit, so that the running cost can be further reduced.

Further, in the brake lining wear detecting device according to the present invention, the amount of reduction of the piston at the time of release of the brake is regulated to substantially reduce the gap between the brake lining and the brake drum when the brake is released regardless of the wear of the brake lining. It is preferable to provide a configuration in which a wheel cylinder having an automatic clearance adjusting device for maintaining the gap is provided, and to provide a signal blocking unit for blocking transmission of the wear detection signal from the detection signal transmitting unit when the brake is operated. With this configuration, the piston is extended even when the brake is released due to the wear of the brake lining. Therefore, even when the brake is released, the wear of the brake lining can be detected. Therefore, the transmission of the wear detection signal is interrupted when the brake is operated, so that the wear detection signal is not transmitted when the amount of extension of the piston increases due to deformation of the brake drum or the like.

It is preferable that the brake lining wear detecting device according to the present invention be provided with a warning means for receiving a wear detection signal from the detection signal transmitting means and performing a warning operation. An alarm lamp (for example, the warning lamp 34 described in the embodiment) is used as an alarm unit.
By using a warning buzzer or the like, a driver or the like can be easily informed of wear of the brake lining.

Further, in the brake lining wear detecting device according to the present invention, the moving member is constituted by a locking member (for example, the left and right clips 25 and 26 described in the embodiment) attached to the piston and the locking member. A telescopic rod that stops and expands and contracts with the expansion and contraction of the piston (for example,
It is preferable to include the left and right rods 12, 13) described in the embodiment. The telescopic rod is held so as to be able to expand and contract with respect to the holding tube, and when the telescopic rod is extended to a predetermined extension amount, the detection signal transmitting means is configured to transmit a wear detection signal. With this configuration, the moving member can be easily moved according to the movement of the piston that expands and contracts. Therefore, even if two pistons are provided in the wheel cylinder, both ends of one holding tube are provided. If the two telescopic rods are expanded and contracted, the moving member can be configured at low cost.

[0014]

Preferred embodiments of the present invention will be described below with reference to the drawings. First, an example of a vehicle drum brake employing the brake lining wear detecting device according to the present invention will be described with reference to FIG. The drum brake 2 includes an axle housing (not shown)
An anchor bracket 30 fixed to the brake shoe unit 20 and holding the brake shoe unit 20;
And a brake drum 40 rotatably disposed with respect to the anchor bracket 30.
This is a so-called wedge type brake in which the brake shoe unit 20 is pressed against the brake drum 40 using a wheel cylinder (also referred to as an actuator) 23 having a wedge as described in detail below.

The brake shoe unit 20 has its base end pivoted by anchor pins 21 and 21 inserted into pin insertion holes 31a and 31a of the support arms 31 and 31 and is mounted to be swingable right and left. Shoe 22, 2
2 The brake shoe 22 includes a support plate 22a made of a steel plate and a lining 22b provided on the support plate 22a. These brake shoes 2
A tension spring 24 is disposed between the distal ends of the brake shoes 22, 22. Normally (when the brake is released), the brake shoes 22, 22 are connected to the tension spring 24.
Are inwardly swung in response to the urging force.

A wheel cylinder 23 is disposed between the tips of the brake shoes 22, 22. As shown in FIGS. 3 and 4, the wheel cylinder 23 includes left and right outer pistons 23 a and 23 b (also referred to as plungers) that are extendable and retractable on the left and right sides, respectively. Are provided with screw adjusters 23c and 23d which are configured to extend (project) outward with respect to the left and right pistons 23a and 23b. A wedge (not shown) is provided between the left and right pistons 23a and 23b (the side opposite to the side on which the screw adjusters 23c and 23d are provided), and by inserting and removing the wedge, the left and right pistons 23a and 23b are inserted.
Respectively expand and contract in the left-right direction. The screw adjusters 23c and 23d have contact portions 22c and 2 formed to protrude inward above the support plates 22a and 22a.
2c is always in contact. Then, by performing the brake operation, the wedge is pushed between the left and right pistons 23a and 23b to extend the left and right pistons 23a and 23b outward in the left and right directions. As a result, the brake shoes 22, 22 resist the tension spring 24 and the anchor pins 21, 22.
The support member 21 is swung so as to extend away from each other, that is, toward the outer peripheral side with the support portion 21 as a center.

A brake drum 40 is disposed outside the brake shoes 22, 22 with an inner surface 40a facing the brake shoes 22. When the brake shoes 22, 22 are swung in the expanding direction as described above, the brake shoes 22 are rotated. , 22 provided on the outer surface of the brake linings 22b, 22b.
a, and the rotation of the brake drum 40 is braked by the frictional force between the two. Thereby, the brake operation of the wheel (not shown) to which the brake drum 40 is attached is performed.

The drum brake 2 has an inner surface 40a of the brake drum 40 and the brake linings 22b, 22b due to wear of the brake linings 22b, 22b.
b, the brake linings 22b, 22b are automatically moved to the brake drum 40 side when the distance between the brake linings 22b, 22b and the inner surface 40a is increased.
An automatic gap adjusting device is provided to keep the gap substantially constant. Various types of adjusting devices are known as such an adjusting device, and detailed description thereof will be omitted. However, the adjusting device having some configurations can be used in the drum brake 2.

Here, the automatic clearance adjusting device provided on the brake drum 2 in the present embodiment will be briefly described.
The automatic clearance adjusting device is provided in the wheel cylinder 23, and when the left and right pistons 23a and 23b extend by a stroke equal to or more than a predetermined stroke (for example, 2 mm) in one braking operation, a predetermined projection amount (for example,
The screw adjusters 23c and 23d protrude from the left and right pistons 23a and 23b by several (100 mm).
Therefore, when the amount of extension of the left and right pistons 23a, 23b increases due to wear of the brake linings 22b, 22b, the braking operation is terminated and the left and right pistons 23a, 23b are stopped.
Even when a and 23b are returned to the positions before the start of the brake operation, the screw adjusters 23c and 23d are located slightly outside without returning to the positions before the start of the brake operation.
The distance between the inner surface 40a and the brake linings 22b, 22b does not extend beyond a predetermined distance.

The drum brake 2 configured as described above
Is equipped with a brake lining wear detecting device 1. As shown in FIGS. 1, 5 and 6, the brake lining wear detecting device 1 is
A mounting member 11 for mounting the holding tube 10 to the wheel cylinder 23; and a left side slidably held in a rod sliding hole 10a formed through the holding tube 10 in the left and right direction. It has a rod 12 and a right rod 13. In addition, the mounting member 11
Is formed with a tube holding hole 11a through which the holding tube 10 can be inserted and held, and can be attached to the wheel cylinder 23 using attachment screws 51, 51.

Here, the left and right rods 12, 13 will be described. Since the left and right rods 12, 13 have the same structure, the left rod 12 will be described below as an example. The left rod 12 includes a protrusion 12a, a sliding portion 12b, and a base 12c.
And extend in the left-right direction and are integrally connected. The protruding portion 12a is formed in a column (round bar) shape extending in the left-right direction, and has a stopper 12 at its left end.
d is attachable, and a sliding portion 12b is formed on the right side of the protruding portion 12a. The sliding portion 12b has a larger outer diameter than the protruding portion 12a, and is formed in a cylindrical shape having an outer diameter that can be slid by being inserted into the sliding hole 10a. Thereby, the left rod 12 slides smoothly in the left-right direction without rattling with respect to the tube 10.

The base portion 12c is provided with a protruding portion 1 from the sliding portion 12b.
2a, the protrusion 12
a and the sliding portion 12b are not formed in a columnar shape, but are formed in a substantially semi-columnar shape as is clear from the plan view in FIG. 5 and the side view in FIG. A guide groove 12e is formed on the upper surface of the base portion 12c, and a dog portion 12f projecting downward is formed on the lower surface. The rod 12 thus formed is placed on the base 1 with the guide groove 12e positioned at the upper part and the dog part 12f positioned at the lower part.
2c and 13c are inserted into the tube 10 together with the rod 13 such that they face each other.

When inserted into the tube 10 as described above, the distal ends of the projecting portions 12a, 13a of the left and right rods 12, 13 project from the left and right ends of the tube 10. The left and right rods 1
After inserting and holding the protruding portions 12a, 13a
Return springs 16 and 17 which are compression coil springs are arranged on the outer periphery of the tube 10, respectively, and bushes 10b and 10b are press-fitted into the left and right ends of the tube 10 in order to hold the return springs 16a and 116b in the tube 10. I do.

In the state where the bushes 10b, 10b are press-fitted, the return springs 16a, 16b
The right and left rods 12, 13 are positioned in the tube 10 in a state of being in close contact with each other by the urging force of b. Note that the left return spring 16a and the right return spring 16b
Are formed with the same biasing force, so that no force is applied to the left and right rods 12 and 13 in FIG.
As shown in FIG. 5 and FIG.
The center in the left-right direction of c is located at the center in the left-right direction of the tube 10 (hereinafter, this position is referred to as “neutral position”). After press-fitting the bushes 10b, 10b in this way, stoppers 12d, 13d are attached to the tips of the protruding portions 12a, 13a, respectively.

The tube 10 holding the left and right rods 12 and 13 in this manner is mounted on the mounting member 11, and a detent screw 11 b is formed on the upper part of the mounting member 11. The tube 10 is provided with a rotation preventing projection insertion hole 10c communicating with the rotation preventing member mounting screw 11b. A detent member 19 is attached to the detent member mounting screw 11b and the detent projection insertion hole 10c. Detent member 19
Is mounted to prevent the left and right rods 12 and 13 from rotating in the tube 10, and has a screw portion 19a screwed to the rotation-stopping member mounting screw 11b and an outer diameter smaller than the screw portion 19a. A projection 19b is formed and extends downward.

Then, by screwing the screw portion 19a to the rotation-stopping member mounting screw 11b, the projection portion 19b passes through the rotation-stop projection insertion hole 10c, and the guide groove 12e,
13e. Thereby, the tube 10 is held by the mounting member 11 and the left and right rods 1
Rotation is prevented while allowing left and right sliding of the tubes 2 and 13 with respect to the tube 10.

A warning switch 18 is mounted on the mounting member 11 on which the tube 10 is mounted. The warning switch 18 includes a switch body 18.
a, a switch actuator 18b extending upward from the switch body 18a, and a contact ball 1 disposed at an upper end of the switch actuator 18b.
8c. Switch actuator 1
The switch 8b is configured to be able to move up and down with respect to the switch body 18a, and is configured to be turned off by a reduction operation (downward movement in FIG. 1).

The warning switch 18 thus configured is inserted into a switch holding hole 11c formed at a lower portion of the mounting member 11, and is mounted using a mounting screw 52. For this reason, in the tube 10, a switch actuator through-hole 10d opening to the switch holding hole 11c is formed, and when the switch 18 is mounted on the mounting member 11, the switch actuator 18b is loosely fitted into the actuator through-hole 10d. When the switch 18 is mounted on the mounting member 11, the contact ball 18c protrudes into the sliding hole 10a.

Further, the contact ball 18c protruding into the sliding hole 10a is located between the dog portions 12f, 13f formed on the left and right rods 12, 13. That is, each dog part 12f, 13f is connected to the base 12c, 13c.
When the left and right rods 12, 13 are in the neutral position, the contact ball 18
c is below the bases 12c and 13c and
f, 13f are located closer to the sliding portions 12b, 13b.
When the left and right rods 12, 13 are in the neutral position, the contact ball 18c does not contact the bases 12c, 13c.

When the left and right rods 12 and 13 move in the left and right directions from the neutral position, the dog portions 12f and 13f of the left and right rods 12 and 13 come into contact with the contact balls 18c and lower the switch actuator 18b. Push down. That is, when the left rod 12 is at the neutral position as shown in FIG. 1, the dog portion 12f is located to the right of the contact ball 18c. Then, for example, when the left rod 12 moves to the left (the left rod extends with respect to the tube 10), the slope 12
g, the contact ball 18c is pushed down and the switch 18 is pressed.
Is turned from ON to OFF, and when the right rod 13 moves rightward, the contact ball 18c is pushed down on the slope 13g of the dog portion 13f to turn off the switch 18.

When the left and right rods 12 and 13 further extend, the contact balls 18c are further pushed down by the bottom surfaces 12h and 13h of the dog portions 12f and 13f, and the warning switch 18 is maintained in the OFF state. Such an OFF operation of the warning switch 18 is performed until the contact ball 18 is again positioned on the slopes 12g and 13g and the switch actuator 18b moves upward by reducing the right and left rods 12 and 13.

The left and right pistons 23 of the wheel cylinder 23
Screw adjusters 23c and 23 in a and 23b
Left and right clips 25 and 26 are attached to d. As described above, in the wheel cylinder 23, the left and right pistons 23a and 23b are respectively extended right and left outward by the brake operation, and the extension causes the brake shoes 22 and 22 to swing in the expanding direction.
Therefore, the left and right pistons 23a, 2
When 3b is extended, the left and right clips 25 and 26 also move in the left and right directions, respectively.

Here, the left and right clips 25 and 26 will be described with reference to FIGS. 3 and 4 again. The left and right clips 25 and 26 are formed in different shapes, but have the same configuration. Therefore, the right clip 26 will be described below as an example. The right clip 26 includes a piston attachment portion 26a attached to the screw adjuster 23d of the right piston 23b, and a piston attachment portion 26a.
a rod connecting portion 26b integrally connected from a and extending leftward
Consists of

The piston mounting portion 26a has a substantially U-shape when viewed from the side, is fitted from below into a screw adjuster 23d formed in a disk shape, and is held while holding the screw adjuster 23d from the front and rear. You. The rod connecting portion 26b has a stopper through hole 26c through which the stopper 13d of the right rod 13 can pass.
And a connection hole 26d which is an elongated hole connected to the stopper through hole 26c and extending upward. Connection hole 2
6d is formed to have a width slightly larger than the outer diameter of the protrusion 13a and a width smaller than the stopper 13d. Then, when connecting the right rod 13 and the right clip 26, the stopper 13d is inserted into the stopper through hole 26c from outside of the right rod 13 so that the protrusion 13a is positioned in the connection hole 26d. Rod 13 and right clip 2
6 is relatively moved. Thereby, the right piston 23b
The rod connecting portion 26b is moved to the projecting portion 13a with the
Can be moved in the left-right direction on the outside.

Here, when the brake operation is not performed,
And in the state where the right rod 13 is in the neutral position,
The rod connecting portion 26b of the right clip 26 is slightly away from the right end of the tube 10 to the right,
It is located at a distance L1 to 3d. Therefore, when the right piston 23b extends, the rod connecting portion 26
b moves to the right, but the right rod 13 remains in the neutral position until the amount of movement reaches the distance L1 to the stopper 13d. Then, when the right piston 23b moves more than the distance L1 and the rod connecting portion 26b further moves rightward after coming into contact with the stopper 13d, the right rod 13 also moves rightward. As described above, when the right rod 13 moves to the right with respect to the tube 10, the contact ball 18c is pushed down by the slope 13g of the dog portion 13f as described above, and the warning switch 18 is turned off.

In the drum brake 2, the amount of extension of the left and right pistons 23a and 23b increases as the brake lining 22b of the brake shoe unit 20 wears. Therefore, when the brake lining 22b reaches the wear limit (for example, the brake lining 22
The amount of extension of the right piston 23b (when the head of the rivet R holding the b is worn) is increased by changing the contact ball 18c by the slope 13g from the state in which the right rod 13 is in the neutral position and the warning switch 18 is turned off. If the distance L2 until the lining 22b reaches the wear limit of the lining 22b, the warning switch 18 can be switched from ON to OFF when the distance L2 equals the distance L2. Therefore, the warning switch 18 is turned off.
For example, when a warning lamp is turned on when an alarm occurs, a warning operation to the driver can be performed.

With the above structure, even if the brake lining 22b is worn, there is no need to replace the wear detecting device 1, and the brake shoe unit 20
Since only the replacement is required, the running cost can be reduced. In the drum brake 2, two brake shoes 22, 22 are provided.
According to the wear detecting device 1 described above, the right and left rods 12 and 13 can be independently extended and contracted, and the warning switch 18 can be operated by operation of any of the rods 12 and 13.
Can be turned off. Therefore, one warning switch 18 allows two brake shoes 2
A warning operation can be performed by detecting wear of the brake linings 22b, 22b.

Next, another embodiment according to the present invention will be described. In the above-described drum brake 2, the switch 18 is turned off by depressing the contact ball 18c as the amount of extension of the left and right pistons 23a and 23b increases.
When it becomes, an alarm is activated. However, in such a configuration, an alarm is also issued when the amount of expansion of the left and right pistons 23a and 23b increases due to expansion of the brake drum 40 due to heat generated during braking and deformation of the brake drum 40 due to pressing of the brake shoe 22. Operation is performed. For this reason, in the present invention, the alarm operation is not performed when the amount of extension of the left and right pistons 23a and 23b is increased due to a cause other than the wear of the brake lining 22b.

When the warning operation is not performed depending on the expansion of the brake drum 40, the warning switch is activated when the right and left rods 12, 13 are extended by the distance L during the brake operation as described above. 18
Rather than setting the shape and dimensions of the rods 12 and 13 so as to turn off, the protrusion amounts of the screw adjusters 23c and 23d when the left and right pistons 23a and 23b return to the original positions after the braking operation is completed are determined by The shape and dimensions of the left and right rods 12 and 13 are set so that the warning switch 18 is turned off when the distance becomes L or more. Therefore,
In this case, even if the brake linings 22b, 22b are not worn, if the left and right pistons 23a, 23b are extended by performing the brake operation, the left and right rods 12, 13 also extend by the distance L or more. When the left and right rods 12 and 13 are extended as described above, the contact ball 18c is connected to the dog portions 12f and 13f.
The warning switch 18 is turned off by being pushed down by the bottom surfaces 12h and 13h.

Here, an electric circuit for turning on a warning lamp when the brake lining 22b is worn will be described with reference to FIG. The electric circuit includes, in addition to the switch 18, a brake switch 31 that is turned on when a brake operation is performed, a brake relay 32 that is energized to the coil when the brake switch 31 is turned on, and a warning switch. When the warning relay 33 energized to the coil when the 18 is in the ON state, the contact 32a of the brake relay 32, and the contact 33a of the warning relay are both ON (closed), the power is supplied from the battery B to light up. And a warning lamp 34. The brake relay 32
When the coil is not energized, the contacts 32a and 33a are in the ON state. When the coil is energized, the contacts 32a and 33a are turned on.
This is a normally closed type relay in which a and 33a are turned off.

According to the electric circuit configured as described above,
If the brake lining 22b is not worn, the warning switch 18 is turned on as described above when the brake operation is completed.
Is turned off, the line on the negative side of the battery B is cut off, and the warning lamp 34 is not turned on. When the brake operation is performed, the left and right pistons 23a, 2a are expanded due to expansion of the brake drum 40 due to heat generated during braking, deformation of the brake drum 40 due to pressing of the brake shoe 22, or wear of the brake lining 22b.
3b, the extension stroke of the left and right rods 12,
Of course, when the extension 13 is extended, the warning switch 18 is turned off and the contact 33a is turned on even when the brake lining 22b is not worn to the wear limit. However, in the state where the brake operation is performed, the brake switch 3 is turned on as shown in FIG.
Since 1 is ON, the contact 32a is turned OFF, the line on the + side of the battery B is cut off, and the warning lamp 34 is not turned on.

As described above, since the drum brake 2 is provided with the automatic adjusting device, when the left and right pistons 23a and 23b extend by a stroke equal to or more than a predetermined stroke in one braking operation, a predetermined amount of protrusion is obtained. As the screw adjusters 23c and 23d protrude, the left and right rods 12 and 13 gradually extend. Then, the brake operation is completed and the left and right pistons 23a, 23
Even if b returns to the original position, the left and right rods 12, 1
Reference numeral 3 denotes a state in which the dog portions 12f and 13f extend in the left and right directions without returning to the neutral position.
7C, when the switch actuator 18b is kept pressed downward, the brake operation is terminated and the warning lamp 34 is turned on when the brake switch 31 is turned off as shown in FIG. 7C. The line from battery B is connected and warning lamp 3
4 lights up.

Therefore, in the drum brake 2, the left and right pistons 23 a and 2 a are temporarily moved by the expansion of the brake drum 40 due to heat generated during the operation of the brake and the deformation of the brake drum 40 due to the pressing of the brake shoe 22.
Even when the amount of extension of 3b increases, the warning lamp 34 does not light up while the brake operation is being performed. The left and right pistons 23 may be temporary.
If the extension amount of the a and 23b is increased, the screw adjuster 2 is used in the same manner as when the brake lining 22b is worn.
Although the protrusions 3c and 23d protrude by a predetermined protrusion amount, the warning lamp 34 does not light due to the expansion or deformation of the brake drum 40 because the protrusion amounts of the screw adjusters 23c and 23d are constant even when the extension amount increases. .

Next, a brake lining wear detecting device 8 having a different structure will be described with reference to FIGS. This brake lining wear detecting device 8 is different from the brake lining wear detecting device 1 in that the brake lining wear
This is to detect the wear of b. For example, the brake lining wear detection device 8 that detects the wear of the brake lining 22b of the right brake shoe 22 includes a holding tube 80 and the wheel cylinder 23
Attachment member 81 for attaching to the holding tube 80
Are formed in a rod sliding hole 80a formed so as to penetrate in the left-right direction. The mounting member 81 is formed with a tube holding hole 81a which is opened to the left and into which the holding tube 80 can be inserted and held, and is connected to the tube holding hole 81a and coaxially opened to the right. A through hole 81b is formed. Further, a dust seal receiving hole 81c is formed on the right end of the mounting member 81 coaxially with the projecting portion through hole 81b, and can be mounted on the wheel cylinder 23 using the mounting screw 53.

The rod 83 includes a projecting portion 83a and a sliding portion 8
3b, extending in the left-right direction and integrally connected. The protruding portion 83a is formed in a columnar (round bar) shape extending in the left-right direction. The right end portion is formed in a hemispherical shape, and the sliding portion 83b is formed on the left side. The sliding portion 83b has a larger outer diameter than the protruding portion 83a, and is formed in a cylindrical shape having an outer diameter that can be inserted into the sliding hole 80a and slidable. Thereby, the rod 83 is connected to the holding tube 80.
It slides smoothly in the left-right direction without rattling. The outer diameter of the center portion 80c in the left-right direction is smaller than the outer diameter near the left and right end portions, and the sliding portion 83b is formed in a substantially drum shape. Here, the central portion 83 of the sliding portion 83b
A slope 83c is formed from c to the left end for the same purpose as the slope 12g of the dog portion 12f.

The rod 83 thus formed is inserted into the holding tube 80 held in the tube holding hole 81a of the mounting member 81, and after the rod 83 is inserted, the return spring 87 is inserted. . After the return spring 87 is inserted, the cap 80e is screwed to the left end of the tube 80 to hold the rod 83 in the holding tube 80 in a state where the rod 83 is urged rightward. Thus, the rod 83 urged by the return spring 87 is in a state where the protruding portion 83a protrudes from the protruding portion through hole 81b. The dust seal 80d is press-fitted and held in the dust seal receiving hole 81c.
a to prevent dust from entering through a gap between the protrusion a and the through hole 81b.

The tube 80 into which the rod 83 has been inserted and held as described above is held by the mounting member 81, and a warning switch 88 is mounted on the mounting member 81. The warning switch 88 is connected to the switch body 8.
8a and a switch actuator 88b extending downward from the switch body 18a. The switch actuator 88b is connected to the switch body 8
8a is configured to be able to move up and down freely, and is configured to be in an OFF state by performing a reducing operation (upward movement in FIG. 8).

The warning switch 88 thus configured is inserted into a switch holding hole 81f formed on the upper part of the mounting member 81, and is mounted using the mounting screw 54. For this reason, a switch actuator through hole 81g that opens in the switch holding hole 81f is formed in the tube 80, and the switch actuator 88b is loosely fitted into the actuator through hole 80f when the switch 88 is mounted on the mounting member 81. When the warning switch 88 is mounted on the mounting member 81, the distal end portion 88c of the switch actuator 88b projects into the slide hole 80a. The distal end portion 88c protruding into the sliding hole 80a is located above the central portion 80c of the sliding portion 83b formed in the rod 83.

Here, as described above, the rod 83 is always urged rightward by the urging force of the return spring 87. In this urged state, the rod 83 protrudes. Side end face is tube holding hole 81a
And is located at the right end where further right movement of the rod 83 is restricted. When the rod 83 is located at the right end in this manner, the slope 83c of the sliding portion 83b abuts on the distal end 88c to cause the switch actuator 88b to operate to reduce the size of the warning switch 8b.
8 is in the OFF state. When the rod 83 is moved to the left by a force opposing the urging force of the return spring 87, the slope 83c is separated from the distal end 88c, the switch actuator 88b is extended, and the warning switch 88 is turned on.

The mounting member 81 to which the warning switch 88 and the holding tube 80 are mounted in this manner is mounted on the wheel cylinder 23 having the same configuration as the wheel cylinder 23 by using the mounting screw 53. Left and right pistons 23a and 23b of the wheel cylinder 23 (FIG. 9)
Shows only the right piston 23a), a left clip (not shown) and a right clip 85, respectively.
Like the left and right clips 25 and 26, they are attached to the screw adjusters 23c and 23d. As described above, in the wheel cylinder 23, the left and right pistons 23a and 23b are respectively extended right and left outward by the brake operation, and the extension causes the brake shoes 22 and 22 to swing in the expanding direction. Therefore, when the left and right pistons 23a and 23b are extended by the brake operation, the right clip 85 and the like also move in the left and right directions.

The right clip 85 includes a piston mounting portion 85a mounted on the screw adjuster 23d of the right piston 23b, and a rod contact portion 85b integrally connected from the piston mounting portion 85a and extending to the left. When the right piston 23b is contracted without brake operation as shown in FIG. 9, the rod contact portion 85b pushes the rod 83 to the left to turn the warning switch 88 on. Is formed.
Then, by performing the brake operation, the right piston 2
When 3b is extended, the right clip 85 also moves rightward, so that the rod 83 also moves rightward. Therefore, the switch 88 can be turned off by moving the rod 83 rightward until the inclined surface 83c abuts on the tip end portion 88c to reduce the switch actuator 88b.

Here, the position from the position of the right clip 85 when the right piston 23b is contracted without brake operation to the position of the right push plate 85 until the warning switch 88 is turned off. If the moving distance is formed to be equal to the distance L, the switch 88 can be turned from ON to OFF when the lining 22b reaches the wear limit, so that a warning is issued by turning on a warning lamp or the like. be able to.

In the above embodiment, the wear of the brake lining 22b of the right brake shoe 22 of the drum brake 2 is detected by detecting the position of the right clip 26 attached to the wheel cylinder 23. I explained the case where
Brake lining 22b of left brake shoe 22
In order to detect the position of the left clip 25, another brake lining wear detecting device constructed in the same manner as the above brake lining wear detecting device 8 is attached to the wheel cylinder 23. Good.

In the above embodiment, the case where the drum brake 2 is a so-called wedge brake has been described. However, as the drum brake, a leading trailing brake or a two-leading brake configured to extend the piston using hydraulic pressure is used. Of course, it may be a brake or the like. Further, the automatic clearance adjusting device does not necessarily need to be provided in the wheel cylinder, and may be separately provided between the two brake shoes. Further, the automatic adjustment of the clearance may be performed not when the normal brake operation is performed (when the service brake is operated) as described above, but when the parking brake is operated or the vehicle is turned back.

[0055]

As described above, the brake lining wear detecting device according to the present invention provides a brake lining when the moving amount of the moving member moving with the extension operation of the piston of the wheel cylinder reaches a predetermined moving amount. Is determined to have worn by a predetermined amount, and a detection signal transmitting means transmits a wear detection signal. Therefore, even when the lining is worn, it is not necessary to replace the brake lining wear detecting device, and only the brake shoe needs to be replaced, so that the running cost of the drum brake can be reduced.

In a drum brake having two brake shoes and two pistons provided in a wheel cylinder, two moving members are provided so as to be movable as the two pistons extend. Preferably, a detection signal transmitting means is provided so as to transmit a wear detection signal when a moving amount of any one of the two moving members reaches a predetermined moving amount. With such a configuration, the wear of the brake linings of the two brake shoes can be detected by one detection signal transmission unit, so that the running cost can be further reduced.

Further, it is preferable that a wheel cylinder having an automatic clearance adjusting device is provided, and that a signal interrupting means for interrupting the transmission of the wear detection signal from the detection signal transmitting means when the brake is operated is provided. With this configuration, the wear detection signal is not transmitted during the operation of the brake. When it becomes larger, the wear detection signal is not transmitted.

In the brake lining wear detecting device according to the present invention, it is preferable to provide a warning means for receiving a wear detection signal from the detection signal transmitting means and performing a warning operation. By doing so, it is possible to easily inform the driver or the like of the wear of the brake lining.

Further, it is preferable that the moving member comprises a locking member attached to the piston, and a telescopic rod which is locked by the locking member and expands and contracts with the expansion and contraction operation of the piston. By doing so, the moving member can be easily moved in accordance with the movement of the piston that expands and contracts. Therefore, even when two pistons are provided in the wheel cylinder, two moving members are provided from both ends of one holding tube. If the telescopic rod is expanded and contracted, the moving member can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a brake lining wear detection device according to the present invention.

FIG. 2 is a front view of a drum brake employing the wear detecting device.

FIG. 3 is a top view of the wear detecting device.

FIG. 4 is a partially enlarged view showing a contact portion between a rake shoe and a right piston in the wear detecting device, wherein a front view is shown in (A), and a BB sectional view in (A) is shown in (B).
Shown in

FIG. 5 is a sectional view of the wear detecting device taken along line VV in FIG. 1;

FIG. 6 is a sectional view of the wear detecting device taken along line VI-VI in FIG. 1;

FIG. 7 is an electric circuit diagram of the wear detecting device.

FIG. 8 is a side view showing another embodiment of the wear detecting device according to the present invention.

FIG. 9 is a sectional view of the wear detecting device taken along line IX-IX in FIG. 8;

[Explanation of symbols]

 1,8 Wear detector 12 Left rod 13 Right rod 18,88 Warning switch 20 Brake shoe unit 40 Brake drum

Claims (5)

[Claims] A brake shoe provided with a brake lining, and a brake drum which is rotatably mounted so as to cover the brake shoe from the outside in the axial direction and to which the brake lining is pressed when a brake is actuated. A device for detecting wear of a lining, comprising a telescopic piston, which is brought into contact with the brake shoe, the piston is extended, and the brake lining is pressed against the brake drum to operate a brake. A wheel cylinder to be moved, a moving member locked to the piston and moving in accordance with the extension operation of the piston, and a brake lining worn by a predetermined amount when the moving amount of the moving member reaches a predetermined moving amount. A detection signal that determines and sends a wear detection signal And a brake lining wear detecting device. 2. The drum brake has two brake shoes, the wheel cylinder is provided with two pistons, and the moving member extends each of the two pistons. The detection signal transmitting means is provided when the movement amount of any one of the two movement members reaches the predetermined movement amount. The brake lining wear detecting device according to claim 1, wherein 3. The wheel cylinder regulates a contraction amount of the piston when the brake is released, and maintains a substantially constant gap between the brake lining and the brake drum when the brake is released irrespective of the wear of the brake lining. 3. An automatic clearance adjusting device according to claim 1, further comprising a signal cut-off means for cutting off transmission of a wear detection signal from said detection signal transmission means when a brake is actuated. The brake lining wear detecting device as described in the above. 4. The brake lining wear according to claim 1, further comprising an alarm unit for receiving an abrasion detection signal from the detection signal transmitting unit and performing an alarm operation. Detection device. 5. The moving member is telescopically held by a locking member attached to the piston and a holding tube, and is locked by the locking member to expand and contract with the expansion and contraction operation of the piston. 5. The telescopic rod according to claim 1, further comprising: a telescopic rod that causes the detection signal transmitting means to transmit the wear detection signal when the detection signal is transmitted to the predetermined extension amount. 6. Brake lining wear detector.