JP2539812Y2 - Spring brake effectiveness drop detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a reduction in the effectiveness of a spring brake in a spring brake system in which a parking brake structure is incorporated into a service brake structure provided on a vehicle wheel.

[0002]

2. Description of the Related Art One of spring brake systems includes:
A brake shoe that comes into sliding contact with a brake drum fixed to the wheel, a brake lining provided on the brake shoe, a piston that expands the brake shoe with hydraulic pressure received by the brake pedal, and a piston that can move forward and backward. A wheel cylinder that supports and operates the piston when the service brake is actuated, a wedge that is movably supported by the wheel cylinder to operate the piston when the parking brake is actuated, and a spring that operates when the parking brake is actuated. Some spring brake chambers include a spring brake chamber for moving the wedge to expand the brake shoe.

[0003] The spring brake chamber includes an air chamber communicated with an air tank, a piston plate slidably provided in the air chamber, a push rod connected to the piston plate, and a brake actuating the piston plate. And a spring that urges in the direction. The push rod is connected to the wedge via an idler lever and a push rod.

When the parking brake is not operated, the spring of the spring brake chamber is compressed by air pressure. When the service brake is operated, the piston expands the brake shoe by hydraulic pressure and presses the brake lining fixed thereto against the brake drum. When the air pressure in the chamber is released during the operation of the parking brake, the piston plate moves by the urging force of the spring, pushes the wedge through a rod or lever connected to the piston plate, and brakes through the piston. The shoe is expanded to push the brake lining against the brake drum. That is, in the spring brake system, the parking brake operation by the manually operated brake lever is executed by the air pressure control and the spring force.

[0005]

In the spring brake system, the parking brake is operated without operating a general parking brake lever, so that the effect cannot be realized. And, since part of the service brake system is used, if the brake lining wears over time, the effectiveness when the parking brake is operated is reduced. In the case of spring brakes, when the air pressure is released, the brakes are immediately actuated by the springs.However, when the lining wears out, the driver operates the service brakes, that is, slowly depresses the brake pedal. While performing the returning operation, it is necessary to perform an operation of confirming whether or not the parking brake is securely applied, and there is a problem that the effect of the spring brake, which is easy to operate, cannot be fully utilized.

Accordingly, an object of the present invention is to provide a device for detecting a decrease in the effectiveness of a brake, which detects the decrease in the effectiveness of a spring brake and improves the reliability of the system.

[0007]

According to the present invention, there is provided a device for detecting a decrease in effectiveness of a spring brake, comprising: a brake shoe slidingly contacting a brake drum fixed to a wheel; a brake lining provided on the brake shoe; A piston to be expanded, a wheel cylinder with a wedge that supports the piston so as to be able to move forward and backward, and activates the piston when a service brake is activated;
A wedge which is supported by the wheel cylinder so as to be able to advance and retreat, and which operates the piston when the parking brake is operated, and a spring brake chamber which expands the brake shoe by moving the wedge by the elasticity of the spring when the parking brake is operated. A spring rod provided with a detection rod integrally connected to a piston plate of the spring brake chamber and having a switch operation circumferential groove formed therein;
The operating piece is brought into contact with the peripheral surface of the detection rod, and when the brake lining is worn and the moving length of the piston plate exceeds a predetermined amount, the operating piece is fitted into the switch operating peripheral groove. And a detection switch that operates.

[0008]

When the brake lining is not worn by a predetermined amount or more, the detection switch cannot be operated because the moving length of the piston plate of the spring brake chamber is also within the predetermined amount. As the wear of the brake lining advances, the amount of movement of the piston plate that moves when the parking brake is actuated increases. When this movement amount becomes a movement length immediately before the parking brake is actuated, the detection switch is moved by the switch operation circumferential groove of the detection rod moved when the parking brake is actuated. Is activated to output a signal that the effectiveness of the spring brake will soon decrease.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

In FIG. 1, reference numerals 1 and 1 denote brake shoes provided inside a brake drum of a wheel (not shown), which are swingable around pins 2 and 2 and which are driven by a spring (not shown). Biased away from On the outer surface of the brake shoes 1, 1, brake linings 3, 3 facing the inner peripheral surface of the brake drum are provided. The outer ends of the pistons 4, 4 are abutted against the respective ends of the brake shoes 1, 1.

The pistons 4, 4 are supported at one end of a wheel cylinder 5 with a wedge so as to be able to advance and retreat. A wedge 6 is fitted to the cylinder 5 so as to be able to move forward and backward, and the tip of the wedge 6 is brought into contact with the pistons 4 and 4. The base end of the wedge 6 is slidably fitted to the cylinder 5 and connected to the push rod 7. The brake oil supply hole 6a of the cylinder 6 is connected to a brake oil line of a service brake system (not shown). When the brake pedal of the service brake system is depressed, the pressure of the brake oil acts on the wheel cylinder 6 to push the pistons 4 and 4 out of the cylinder, expand the brake shoes 1 and 1, and apply the brake linings 3 and 3 to the brake drum. A brake force is generated by pressing and sliding on the inner peripheral surface.

The push rod 7 is connected to one end of an idler lever 8 provided so as to be swingable. One end of a push rod 10 of a spring brake chamber 9 is pivotally connected to the other end of the idler lever 8.

The other end of the push rod 10 of the spring brake chamber 9 is connected to a piston plate 11 which forms an air chamber 9a with the chamber. Air chamber 9
a is connected to a spring brake tank 13 via an air pipe 12. A relay valve 14 is provided in the middle of the air pipe 12. A spring 15 is provided between the piston plate 11 and the bottom of the chamber 9 to urge the push rod 10 in a pushing direction.

The control air pipe 16 between the spring brake tank 13 and the relay valve 14 is provided with a control valve 17 disposed in the driver's seat.
The spring brake tank 13 includes a check valve 18
Is connected to the reservoir tank 19 via the.

When the service brake system is activated, the air chamber 9a of the chamber 9 contains the tank 1
The air pressure from 3 is supplied to push down the piston plate 11 against the elasticity of the spring 15. When the plate 11 is pressed down, the wedge 6
Is moved to the left in the cylinder 5.

A detection rod 20 is connected to the piston plate 11 on a surface opposite to the push rod 10. A detection switch 21 is in contact with the peripheral surface of the rod 20. The switch 21 is connected to the controller 2
2 are connected. The controller 22 is connected with an alarm lamp 23 for notifying that the effectiveness of the parking brake is reduced. A detecting device 24 for detecting a drop in the effectiveness of the spring brake by the detection rod 20 and the detection switch 21
Is composed.

In FIG. 2, the detection rod 20 is integrally connected to the piston plate 11. Rod 2
0 is slidably inserted into the switch holder 25. The detection rod 20 has a circumferential groove 20 for switch operation.
a is formed. The detection switch 21 is fixed to and held by the switch holder 25, and has an operating piece 21 a having a protruding behavior in contact with the peripheral surface of the detection rod 20.

FIG. 2 shows a state where the parking brake system is not operated. In this state,
The detection rod 20 has its switch-operating circumferential groove 20a located at a distance L from the operating piece 21a. The movement length of the detection rod 20 that moves when the parking brake system is operated is shorter than the distance L when the wear of the brake lining 3 is small, and gradually becomes longer as the wear of the lining progresses.

The operation of the embodiment configured as described above will be described. In FIG. 1, when the parking brake system is not operated, air pressure from the spring brake tank 13 is applied to the air chamber 9 a of the spring brake chamber 9 via the relay valve 14, and the piston plate is opposed to the spring 15. 11 is down. The movement of the plate 11 is transmitted to the wedge 6 via the push rod 10, the idler lever 8 and the push rod 7 connected to the plate 11, and the wedge 6 is positioned at the left end of the wheel cylinder 5. It does not hinder the operation of the brake system. When the brake pedal of the service brake system is depressed in the state shown in FIG. 1, the pressure of the brake oil is transmitted to the cylinder 5 from the brake oil supply hole 6a. This hydraulic pressure acts to push the pistons 4, 4 out of the cylinder 5 to expand the brake shoes 1, 1. The expanding brake shoes 1,1 are
The brake linings 3 and 3 are brought into sliding contact with a brake drum inner peripheral surface (not shown). When hydraulic pressure is supplied to the cylinder 5, the wedge 6 remains at the position shown.

To operate the parking brake system, the control valve 17 in the driver's seat is operated to operate the relay valve 14 in a direction to release the air chamber 9a of the chamber 9 to the atmosphere. When the relay valve 14 releases the air chamber 9a to the atmosphere, the piston plate 11
The push rod 10 is pushed up by the elasticity of 5, and moves the push rod 10 connected thereto. Push rod 10
Is transmitted to the push rod 7 via the idler lever 8, and pushes the wedge 6 rightward in the figure. The pushed wedge 6 pushes the pistons 4, 4 out of the cylinder 5 at the wedge portion at the tip end thereof, thereby expanding the brake shoes 1, 1. The expanding brake shoes 1, 1 press the brake linings 3, 3 fixed thereto to the inner peripheral surface of the brake drum to prevent the wheels from rotating.

When the piston plate 11 moves, the detection rod 20 connected to the piston plate 11 also moves at the same time. The moving length of the detection rod 20 is short when the wear amount of the brake linings 3 and 3 is small, and increases as the wear progresses and the so-called shoe gap between the brake drum and the brake lining increases. The limit of the shoe gap determined by the wear amount of the brake lining is replaced by the moving length L of the detection rod 20. Therefore, brake lining 3,
If the wear of No. 3 is equal to or less than a predetermined amount and the shoe gap is within a predetermined value, when the parking brake system is operated, the detection rod 20 moves within the range of the distance L. In this state, the parking brake operates stably and reliably.

When the wear of the brake linings 3 and 3 progresses, and immediately before the limit at which a predetermined shoe gap can be maintained, the movement amount of the piston plate 11 when the parking brake system is operated becomes large. Accordingly, the detection rod 20 is also largely moved. That is, when the brake linings 3 and 3 are worn and the piston plate 11 moves to a predetermined length L or more, the switch operating piece 21a is fitted into the switch operating circumferential groove 20a of the detection rod 20 and the detection switch 21 is turned on. Actuated. The operation of the switch 21 is input to the controller 22 as a signal for notifying that the effectiveness of the parking brake is reduced. The controller 22 that has received this signal turns on the alarm lamp 23. Warning lamp 2
The driver who sees the lighting of 3 recognizes that the effectiveness of the parking brake will soon decrease. In other words, when the alarm lamp 23 is turned on, it means that the brake lining 3 has been worn, and the effectiveness of the service brake and the spring brake serving as the parking brake is also reduced. You have foretold.

In the illustrated embodiment, the detection rod 20 is directly connected to the piston plate 11, but a part that moves linearly with the plate, for example, a part of the push rod 10 protruding from the air chamber 9a is connected to the detection rod 20. You may use as.

[0024]

As described above, according to the present invention, since the wear state of the brake lining is detected from the stroke of the spring brake chamber for operating the parking brake, it is possible to know at an early stage that the effectiveness of the parking brake has decreased. It is possible to operate the parking brake in an uneasy state. Further, since the wear of the brake lining can be detected without depending on the traveling distance, it is possible to know the arrival of the maintenance time for the service brake.

[Brief description of the drawings]

FIG. 1 is a system diagram of a spring brake system showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Brake shoe 3 ... Brake lining 4 ... Piston 5 ... Wheel cylinder 6 ... Wedge 9 ... Spring brake chamber 10 ... Push rod 11 ... Piston plate 15 ...・ Spring 20 ・ ・ ・ Detecting rod 20a ・ ・ ・ Switching peripheral groove 21 ・ ・ ・ Detecting switch 21a ・ ・ ・ Activating piece 23 ・ ・ ・ Alarm lamp

Claims (1)

(57) [Scope of request for utility model registration] A brake shoe slidingly contacting a brake drum fixed to a wheel; a brake lining provided on the brake shoe; a piston for expanding the brake shoe; A wheel cylinder with a wedge that activates the piston when the service brake is activated, a wedge that is movably supported by the wheel cylinder and that activates the piston when the parking brake is activated, and the wedge that is resilient by a spring when the parking brake is activated. And a spring brake chamber for expanding the brake shoe by moving the spring brake chamber. The spring brake is integrally connected to a piston plate of the spring brake chamber, and has a switch operating peripheral groove formed therein. And the operating piece is brought into contact with the peripheral surface of the detecting rod. When the brake lining wears out and the moving length of the piston plate exceeds a predetermined amount, the switch operating A device for detecting a reduction in the effectiveness of a spring brake, comprising a detection switch which is fitted into a circumferential groove and operated.