JPH0711304B2 - Friction brake usage limit sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a friction brake usage limit sensor, and more specifically, to a usage caused by wear of a friction pad (hereinafter, also used as a concept including a lining). The present invention relates to a friction brake usage limit sensor that can detect not only the limit but also the usage limit due to temperature conditions.

<Prior Art> Since the friction brakes equipped on various vehicles are in a state in which reliable braking performance cannot be exerted, an accident such as a collision occurs, and in the worst case, it may result in a personal injury.
It is necessary to inspect and replace the wear state of the friction pad at every predetermined traveling distance.

However, it is not only the wear state of the friction pad that causes the friction brake to exhibit the desired braking performance, but also the working fluid receiving space for moving the movable body to press the friction pad against the braked body. Poor pressure resistance, liquid leakage, vapor lock of working fluid, fade of friction pad, etc. will cause deterioration of braking performance.

Therefore, it is required to constantly monitor the occurrence state of each of the above causes in the running state of the vehicle, and in order to satisfy this requirement, a bimetal is installed at an appropriate position of the sensor body to detect the temperature of the working fluid. It has a movable piece that is pressed against the piston.When the piston moves due to wear of the friction pad, the movable piece pressed against the piston moves, and at this time the contacts are released or short-circuited. A structure that can detect the wear limit has been adopted (Japanese Patent Application Laid-Open No. Sho.
59-183126).

According to this configuration, when the wear amount of the friction pad reaches a predetermined amount, the usage limit due to the wear is detected, and the bimetal is activated when the temperature of the friction pad is increased due to a fade of the friction pad. It is possible to detect a usage limit due to a fade or the like.

<Problems to be Solved by the Invention> In the configuration described above, since the movable piece in which the piston moves and the piston is no longer pressed receives the pressure of the working fluid directly, it acts on the movable piece each time the brake is turned on. The contact pressure is short-circuited or released due to the fluid pressure, and the warning lamp that is lit up is extinguished each time.

This invention has been made in view of the above problems,
A friction brake that can detect not only the operating limit due to wear of the friction pad, but also the operating limit caused by vapor lock of the working fluid and fade of the friction pad, and can give a reliable warning to the driver. It is intended to provide a usage limit sensor.

<Means for Solving Problems> A friction brake usage limit sensor of the present invention for achieving the above object is attached to a caliper body, and includes a sensor casing, a movable electrode member, and a fixed electrode member. And an auxiliary electrode member forming a part thereof.

The caliper body has a space for supplying a working fluid at a predetermined position, and movably supports a piston for pressing a friction pad inside the space.

The sensor casing has a cylindrical shape in which the rear end of the piston is fixed at a desired position.

The movable electrode member slides in the sensor casing, follows the movement of the piston, and moves to a predetermined position to come into contact with or release the contact with the fixed electrode member.

The fixed electrode member is fixed in the sensor casing,
When the movable electrode member follows the movement of the piston and moves in the movement axis direction of the piston to reach a predetermined position, the movable electrode member contacts or is released from the movable electrode member.

The auxiliary electrode member is made of a shape memory alloy, constitutes a part of the fixed electrode member, and selects a contact state or a non-contact state with the movable electrode member depending on the temperature.

The movable electrode member is provided with a communication hole that allows the working fluid in the cylinder chamber to communicate with the inside of the sensor casing.

<Operation> In the case of the friction brake use limit sensor having the above configuration, the working fluid is supplied to the space of the caliper main body to move the piston and press the friction pad against the braked object. When exerting the braking performance, both the fixed electrode member and the auxiliary electrode member come into contact with the movable electrode member unless the usage limit has been reached due to wear of the friction pad, vapor lock of the working fluid, fade of the friction pad, etc. However, either the contact state or the non-contact state (which is set in advance in advance) causes the predetermined electric circuit to be in a conductive state or a cutoff state in accordance with the set state, and the friction brake It is possible to detect that the usage limit has not been reached.

When the wear amount of the friction pad reaches a predetermined amount, the fixed electrode member and the movable electrode member come into contact with each other or are released from each other, so that it is possible to detect that the friction brake has reached the use limit.

Further, when the vapor lock of the working fluid and the fade of the friction pad occur, the electric connection between the fixed electrode member and the movable electrode member remains in a state where the use limit of the friction pad is not reached, but It is possible to detect that the auxiliary electrode member made of a shape memory alloy, which constitutes a part of the electrode member, comes into contact or non-contact with the inner surface of the fixed electrode member, and the friction brake has reached the limit of use.

In the above description, the contact / non-contact state between the fixed electrode member and the movable electrode member and the contact / non-contact state between the auxiliary electrode member and the movable electrode member are separately generated. However, the same operation can be performed even when only the contact or non-contact state between the auxiliary electrode member and the movable electrode member occurs.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 1 is a schematic vertical cross-sectional view showing a main part of a friction brake incorporating the friction brake use limit sensor of the present invention. The friction brake use limit sensor () is provided at a predetermined position of a caliper body (1) made of a conductive material. 2) is incorporated, and the friction pad (4) is brought into pressure contact with the disc rotor (5) by the piston (3) reciprocally attached to the caliper body (1).

More specifically, a cylinder chamber (6) having one end opening to the outside is formed at a predetermined position of the caliper body (1), and a piston (3) reciprocates to close the opening of the cylinder chamber (6). It is movably installed. A piston seal (7) is attached at a predetermined position of the opening of the cylinder chamber (6).

The cylinder chamber (6) of the caliper body (1)
A friction brake use limit sensor (2) is attached with a position where it communicates with the inner back part of the, with an O-ring (8) interposed.

The friction brake usage limit sensor (2) is a holding member (22) made of an insulating material fixed in a predetermined position of a cylindrical sensor casing (21) made of a conductive material.
A movable electrode member having a fixed electrode member (23) attached thereto and having a communication hole (25a) in the center urged by a spring (24) to lightly follow the cylinder chamber (6) side. (25) is mounted slidably. The spring (24) has a light spring load and an extremely low spring constant to the extent that the retraction function of the piston (3) is not hindered. Then, the movable electrode member (2
5) Auxiliary electrode member made of a shape memory alloy which is separated from (see FIG. 2A) and which is in a stretched state at high temperature and comes into contact with the inner surface of the movable electrode member (25) (see FIG. 2B). (26) is attached, and further, an inward flange portion (28) is formed in the opening of the recess (27) formed on the fixed electrode member side of the movable electrode member (25), and the movable electrode by the spring (24) is formed. When the movement amount of the member (25) reaches a predetermined amount, the auxiliary electrode member (26) and the inward flange portion (28) are brought into contact with each other (see FIG. 3). A power source (29) and an indicator lamp (30) are connected in series between the fixed electrode member (23) and the caliper body (1).

The operation of the friction brake having the above structure is as follows.

When the working fluid is supplied to the cylinder chamber (6) through the liquid supply passage (not shown) of the caliper body (1), the piston (3) moves and the friction pad (4) is pressed against the disc rotor (5), The plate rotor (5) can be braked.

In this case, when the friction pad (4) is not worn so much, the auxiliary electrode member (26) and the inward flange (28) of the movable electrode member (25) are not in contact with each other (first (See Figure 1). If neither vapor lock of the working fluid nor fade of the friction pad occurs, the temperature does not rise so much, so the auxiliary electrode member (26) at the tip of the fixed electrode member (23) is , Is still held in a wound state (see FIG. 2A) and is also in a state of being separated from the inner surface of the movable electrode member (25).

Therefore, the indicator lamp (30) is not energized, and it can be identified that the friction brake has not reached the use limit state.

Further, when either the vapor lock of the working fluid or the fade of the friction pad occurs, the temperature rises abnormally, so that the auxiliary electrode member (26) is in an extended state (see FIG. 2B), and the movable electrode It is possible to identify that the friction brake has reached the limit of use by contacting the inner surface of the member (25) and energizing the indicator lamp (30).

Furthermore, when the wear amount of the friction pad (4) reaches a predetermined amount, the movement amount of the movable electrode member (25) by the spring (24) reaches a predetermined amount, so that the auxiliary electrode member (26) moves to the second position. Figure A
Even if the auxiliary electrode member (26) is held in the wound state as shown in FIG.
Since it comes into contact with the inward flange portion (28), it is possible to identify that the indicator lamp (30) is energized and the friction brake has reached the use limit.

FIG. 4 is a longitudinal cross-sectional view of a main part showing another embodiment. The difference from the above embodiment is that the opening of the recess (27) of the movable electrode member (25) has an inward flange portion (28). Instead of forming the insulating seal portion (31), the auxiliary electrode member (26) becomes a winding state at a high temperature and is separated from the movable electrode member (25) (see FIG. 2A), and at a low temperature. Sometimes it is in an extended state and contacts the inner surface of the movable electrode member (25) (second
(Refer to FIG. B) It is only the point constituted by the shape alloy.

Therefore, also in the case of this embodiment, the movable electrode member (2
It is possible to identify whether or not the friction brake has reached the usage limit based on the contact state or non-contact state between the 5) and the auxiliary electrode member (26). In the case of this embodiment, since the electrical contact between the movable electrode member (25) and the auxiliary electrode member (26) is cut off when the friction brake reaches the limit of use, the sensor drive If a failure occurs in the system and normal detection cannot be performed, the same indication as when the usage limit is reached will be displayed. Check the friction pad (4) and sensor drive system. As it will be urged, the safety can be improved.

Note that the present invention is not limited to the above-described embodiment, and for example, when the wear amount of the friction pad reaches a predetermined amount, the positional relationship between the fixed electrode member and the movable electrode member is different from the contact state and the contact state. The positional relationship between the auxiliary electrode member and the movable electrode member only when the contacting state is established (however, the state is set in advance in advance), and the vapor lock of the working fluid and the fade of the friction pad occur. Can be configured to be in either a contact state or a non-contact state (provided that the state is set in advance in advance), and various other configurations are possible without changing the gist of the present invention. It is possible to change the design of.

<Effects of the Invention> As described above, the present invention can not only detect the usage limit due to wear of the friction pad, but also reliably detect the usage limit due to the vapor lock of the working fluid and the fade of the friction pad. In addition, by exchanging the worn friction pad, there is a unique effect that it can be used repeatedly.

Furthermore, since the movable electrode member is provided with a communication hole that allows the working fluid in the cylinder chamber to communicate with the inside of the sensor casing, the movable electrode member itself is not affected by the brake on / off, that is, the pressure of the working fluid. It is possible to prevent malfunctions and malfunctions.

Further, since the friction brake use limit sensor of the present invention is fixed at a position where the rear end of the piston existing in the cylinder chamber of the caliper body is desired, it is not necessary to attach or detach the friction brake use limit sensor when replacing the friction pad.

Further, as in the invention according to claim 3, when the movable electrode member moves to a predetermined position, the contact with the fixed electrode member is released, and the auxiliary electrode member does not contact the movable electrode member when the temperature rises. In the case where the sensor itself has a disconnection failure, etc., the same action as that when the usage limit of the friction brake is generated can be obtained, and the safety can be improved.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a main part of a friction brake incorporating the friction brake use limit sensor of the present invention, FIG. 2 is a view showing a relationship between a movable electrode member and an auxiliary electrode member, and FIG. FIG. 4 is a schematic vertical sectional view showing a state where the friction pad is worn to the limit of its use, and FIG. 4 is a longitudinal sectional view of an essential part showing another embodiment. (1) ... caliper body, (2) ... friction brake usage limit sensor, (3) ... piston, (4) ... friction pad, (5) ... disk rotor, (6) ... cylinder chamber , (23) ... fixed electrode member, (24) ... spring, (25) ... movable electrode member, (26) ... auxiliary electrode member, (25a) ... communication hole

Claims (3)

[Claims] 1. A caliper main body having a space to which a working fluid is supplied, and a caliper body which is moved into the space by the pressure of the working fluid,
In a friction brake including a piston that presses a friction pad held at a predetermined position against a braked body, a cylindrical sensor fixed at a desired position with a rear end portion of the piston existing in a cylinder chamber of the caliper body. A movable electrode member slidable in the sensor casing so as to always contact the casing and the rear end of the piston, and the movable electrode member fixed in the sensor casing. The movable electrode member follows the movement of the piston to move the piston. A fixed electrode member that moves in the axial direction and comes into contact with or is released from the movable electrode member when reaching a predetermined position, and a movable electrode member that constitutes a part of the fixed electrode member and is dependent on temperature. An auxiliary electrode member made of a shape memory alloy for selecting a contact state or a non-contact state with respect to the sensor case, the working fluid in the cylinder chamber being supplied to the movable electrode member. Friction brake usage limit sensors, characterized in that the communicating hole for communicating to the grayed is provided. 2. The movable electrode member comes into contact with the fixed electrode member when moved to a predetermined position, and the auxiliary electrode member comes into contact with the movable electrode member when the temperature rises. The friction brake usage limit sensor according to the first item. 3. The movable electrode member is released from contact with the fixed electrode member when moved to a predetermined position, and the auxiliary electrode member is brought into non-contact with the movable electrode member when the temperature rises. The friction brake usage limit sensor according to claim 1.