JPH0520613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in brake safety devices for automobiles, railway vehicles, etc., and is applied to brake fluid temperature detection and brake lining wear limit detection. This relates to temperature and wear sensors.

Structure of a conventional example and its problems FIG. 1 shows a cross-sectional view of a disc brake equipped with a conventional brake lining wear limit sensor, and FIG. 2 shows an enlarged cross-sectional view of the vicinity of this sensor. In FIG. 1, 1 and 1a are brake linings, and 2 and 2a are back metals. When the piston 4 in the cylinder 3 is moved by the hydraulic pressure of the brake fluid 5, the rotor 6 is moved from both sides to the brake linings 1 and 2a. 1a, and a braking action occurs due to the frictional force generated at the contact surface. Therefore, if the sensor 7 is installed in the brake lining 1 (or 1a), when the brake lining 1 wears out due to friction with the rotor 6, the tip of the sensor 7 will also be scraped, so this fact can be utilized. Thus, the wear limit of the brake lining 1 can be detected.

Next, details of detecting the wear limit of the brake lining 1 will be explained with reference to FIG. 2. In FIG. 2, 8 is a metal wire, 9 is a case, and 10 is an external lead wire, which constitutes the sensor 7. This sensor 7
is embedded in the brake lining 1 via the metal backing 2, so when the brake lining 1 wears out and is scraped from the initial position A to the limit position B, the sensor 7 is also scraped together and the metal wire 8 is The wire breaks. At this time, the resistance of the sensor 7 seen from the external lead wire 10 changes from zero to infinity, and the wear limit of the brake lining 1 can be detected.

However, this sensor only detects the wear limit of the brake lining and has the disadvantage that it is disposable.

On the other hand, from the safety aspect of the brake system, we are trying to prevent paper lock (a condition in which the brake fluid becomes abnormally hot, causing air bubbles to form inside the brake fluid and making the brakes ineffective), which occurs when the brakes are used continuously, especially when going downhill. In order to prevent this, there is a strong demand for a sensor that can also detect abnormal temperature rises in brake fluid.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a temperature and wear degree sensor that has both the functions of detecting the wear limit of a brake lining and detecting an abnormal temperature rise of brake fluid.

Structure of the Invention The structure of the present invention has a heat-sensitive element for detecting an abnormal temperature rise in brake fluid, and a movable metal piece that presses a piston in a brake cylinder. The metal movable piece is structured to fall off the piston when the piston moves, and at this time, the contact integrated with the metal movable piece separates from the coil spring fixed to the external lead terminal and becomes electrically open. Accordingly, the brake lining is constructed with a mechanism that also detects the wear limit of the brake lining.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment of the present invention. In FIG. 3, reference numeral 11 denotes a temperature and wear degree sensor according to the present invention, which is installed in the brake cylinder 3 at a position where it comes into contact with the brake fluid 5 and the piston 4.

Next, FIG. 4, which is an enlarged sectional view of the temperature and wear degree center according to the present invention, will be explained. A heat-sensitive element 18 (for example, a thermistor) that detects the temperature of the brake fluid 5 is installed in a vertically movable metal movable piece 21 that presses the piston 4 that moves due to wear of the brake lining, and heat is applied to the vicinity of the heat-sensitive element 18. It is filled with a resin 22 having excellent conductivity. Further, one lead wire of the heat-sensitive element 18 is soldered 24 to the metal movable piece 21, and the other lead wire is soldered 23 to the contact 16 attached to the metal movable piece 21 via an insulator 19. . Further, the contact 16 is electrically connected to the external lead terminal 14 when the metal movable piece 21 is pressing the piston 4 by a second coil spring 15 fixed to the external lead terminal 14. . Further, the metal movable piece 21 is electrically connected to the metal case 12 by the first coil spring 20 and is given a force to press the piston 4 . The sliding surface between the side surface of the metal movable piece 21 and the metal case 12 is sealed with a sealing material 17 so that the brake fluid 5 does not enter inside. Further, 13 and 14 are an insulator and a metal plate, respectively.

Next, the operating principle will be explained. In the brake temperature and wear sensor 11 according to the present invention, the tip of the metal movable piece 21 contacts the piston 4 in the brake cylinder 3, and the metal movable piece 21 is lifted by the piston 4, and the contact 16 is in contact with a second coil spring 15 fixed to the external lead terminal 14. At this time, since the heat-sensitive element 18 is connected in series between the external lead terminal 14 and the metal case 12, an abnormal temperature rise in the brake fluid 5 can be detected. On the other hand, as the brake linings 1 and 1a wear out, the piston 4 moves leftward from the initial position c, and when it reaches the limit position D, the metal movable piece 21 moves towards the first coil spring 2.
0 moves it downward. Here, if the tip position of the second coil spring 15 when free is located above the position of the contact 16 and a space is created between the two, the external lead terminal 14 and the metal case 12 can be electrically connected. By opening the brake linings 1 and 1a, the wear limit of the brake linings 1 and 1a can be detected.

Effects of the Invention As explained above, according to the temperature and wear degree sensor of the present invention, a single sensor has both the functions of detecting brake fluid temperature and brake lining wear degree detection, and is not disposable but semi-permanent. It also has the feature that it can be used for. Furthermore, since it is a normally closed contact system, if there is a break at any point inside or outside the sensor, the condition will be the same as when the brake lining is worn out, and conversely, if there is a short circuit, the thermistor will act as a heat-sensitive element. If an element having negative resistance-temperature characteristics such as the above is used, the brake fluid will be in the same state as when the temperature rises abnormally, and has a feature of having a fail-safe function. Moreover, it has an extremely simple configuration and can be provided at low cost.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional disc brake equipped with a brake lining wear limit sensor, and Figure 2 is an enlarged cross-sectional view of the vicinity of this sensor.
FIG. 3 is a sectional view showing one embodiment of a disc brake with a temperature and wear sensor according to the present invention;
The figure is an enlarged cross-sectional view of the vicinity of the same temperature and wear rate sensor. 1, 1a... Brake lining, 3... Cylinder, 4... Piston, 5... Brake fluid, 6...
...Rotor, 11...Temperature, degree of wear sensor, 12...
...Metal case, 14...External extraction terminal, 15...
2nd coil spring, 16... Contact, 18... Heat sensitive element, 20... First coil spring, 21... Metal movable piece.

Claims (1)

[Claims] 1. A heat-sensitive element that detects the temperature of brake fluid is installed inside a movable metal piece that presses a piston that moves due to wear of the brake lining, and one lead wire of the heat-sensitive element is connected to the metal movable piece. The other lead wire is attached to a contact attached to the metal movable piece through an insulator, and the metal movable piece is electrically connected to the metal case by the first coil spring and the piston is connected to the metal case. A pressing force is obtained, and when the metal movable piece moves into the metal case by a predetermined amount or more by a second coil spring fixed to the external lead terminal, the contact point is electrically connected to the external lead terminal. Temperature and wear of the brake characterized by having a structure in which the contact point and the second coil spring separate when the metal movable piece moves out of the metal case by a predetermined amount or more. degree sensor.