Brakes – Wheel – Transversely movable
Reexamination Certificate
2000-10-19
2001-12-11
Butler, Douglas C. (Department: 3613)
Brakes
Wheel
Transversely movable
C188S079540, C188S1960BA
Reexamination Certificate
active
06328141
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
This invention relates to a drum brake device with an automatic shoe clearance adjustment device for a motor vehicle and, more specifically, to a means to prevent over-adjustment operation of the automatic shoe clearance adjustment device.
2. Description of Related Art
Conventional means to prevent over-adjustment of shoe-to-drum clearances with the automatic shoe clearance adjustment device may broadly be known in the following two types of different means.
For example, as a first type, the Japanese Patent Application Publication Numbers 57-8975 and 2-15737 disclose one means disabling automatic adjustment operation of shoe-to-drum clearances by inhibiting a rotation of an adjustment lever, when an actuating force to separate brake shoes apart, reaches a predetermined magnitude.
As a second type, the U.S. Pat. Nos. 4,385,681, 4,390,086, and German Patent Application Unexamined Publication Number 3100678 disclose another means disabling automatic adjustment operation of the shoe-to-drum clearances by thermally deforming a bimetallic piece when a brake temperature rises up to the certain degree.
However, both conventional means have various problems as stated below when the respective means is used independently.
Recently, in terms of an effective use of a rear braking force, automobile industries tend to increase the number of motor vehicles with the Electronic Brakeforce Distribution (EBD) system which is intended to provide the most effective braking force distribution in relation to the front and rear braking forces. A vehicle with the EBD system is characterized in that the rear braking force is adapted to be stronger (higher) than that of a conventional vehicle equipped with a hydraulic pressure control valve, i.e., a pressure proportioning valve, a deceleration responsive valve, and a load sensitive proportioning valve.
Due to the fact that the higher load is placed on the rear brake of the vehicle with the EBD system than that of the vehicle without the EBD system, higher thermal energy is generated during the braking operation.
To achieve the required shoe-to-drum clearances under high load and temperature, the shoe-to-drum clearances must be a bit larger than an ideal value during the normal use if one of the above-two means to prevent over-adjustment is employed independently. As a result, if the shoe-to-drum clearances become smaller than the setting, it is less likely to cause a problem of dragging. Although it is possible to prevent the over-adjustment of the shoe-to-drum clearances by designing the shoe-to-drum clearances to be larger during the normal use, it automatically leads to a longer pedal stroke giving an uncomfortable feeling to the driver.
As a general strategy to deal with the above-problems in relation to the high load and high temperature condition, it is known that a diameter of the brake drum may be designed to be larger, which also enlarges the size of drum brake itself. While an enlarged brake may resolve the above-problems, the enlarged brake generally causes other problems of providing a heavier device, an environmentally problematic device, and a high energy consuming device. These problems lead to the need for making an improvement without enlarging the size of the brake.
OBJECT AND SUMMARY OF THE INVENTION
This invention is made to improve upon the above drawbacks noted in the prior art, and an object of this invention is to provide a drum brake device with an automatic shoe clearance adjustment device realizing the long-lasting assurance in the appropriate operation of preventing over-adjustment of the shoe-to-drum clearances even under the high load and temperature condition. Further an object of this invention is to provide a drum brake device with an automatic shoe clearance adjustment device minimizing its size and improving the feeling of the braking action without sacrificing the optimum shoe-to-drum clearances.
To the above-ends, this invention is a drum brake device with an automatic shoe clearance adjustment device, which extends between a pair of adjacent ends of facing brake shoes. The device comprises a restricting means for restricting return positions of the brake shoes and for displacing automatically the brake shoes in a separation direction to separate each brake shoe when the shoe-to-drum clearances exceed predetermined value. The automatic shoe clearance adjustment device further has a preventing means to prevent an over-adjustment of the shoe-to-drum clearances by inhibiting displacement of the brake shoes in the separation direction to separate each brake shoe due to the restricting means when at least one of an actuating force to separate the pair of brake shoes reaches the predetermined magnitude or a temperature in the drum brake rises up to the certain degree.
This invention further provides a drum brake device with an automatic shoe clearance adjustment device, wherein the restricting means comprises a screw mechanism and adjustment teeth, and when the amount of rotational movement of an adjustment lever which automatically senses an excessive brake shoes separation exceeds one tooth pitch of the adjustment teeth, the adjustment lever urges the adjustment teeth into rotation resulting in length extension of the screw mechanism and displacement of the brake shoes in the separation direction to separate each brake shoe.
This invention still further provides a drum brake device with an automatic shoe clearance adjustment device, wherein the adjustment lever is pivotally supported on one brake shoe for the rotation relative to the one brake shoe. The adjustment lever has two legs, and due to an urging force of an adjustment spring, a first leg extending from a pivot section of the adjustment lever is urged to be elastically engaged with one end of the restricting means while a second leg also, but oppositely extending from the pivot section of the adjustment lever is urged to be ratchet-engaged with the adjustment teeth.
This invention still further provides a drum brake device with an automatic shoe clearance adjustment device, wherein the adjustment lever is pivotally supported on one brake shoe for rotation relative to one brake shoe. The adjustment lever has two legs, and due to urging force of an adjustment spring, a first leg extending from a pivot section of the adjustment lever is urged to be elastically engaged with one end of an engagement piece integrally acts with a piston, a device to displace the brake shoes, while second leg also but oppositely extending from the pivot section of the adjustment lever is urged to be ratchet-engaged with the adjustment teeth.
This invention still further provides a drum brake device with an automatic shoe clearance adjustment device, wherein the adjustment lever is integrally provided with a force sensing section responsive to a brake shoe action and a bimetallic thermal sensing section responsive to a temperature within a drum brake. The force sensing section and the bimetallic thermal sensing section function as a means to prevent over-adjustment operation of shoe-to-drum clearances.
This invention still further provides a drum brake device with an automatic shoe clearance adjustment device wherein a force sensing section responsive to brake shoe action is extended from a pivot section of the adjustment lever and is positioned so as to be rotatable in the crossing direction of an axial line of a brake shoe actuating device. When a force acting on the force sensing section from the actuating device becomes stronger than an urging force of the adjustment spring effecting thereon, the adjustment lever is restricted to rotate by sandwiching the force sensing section between the actuating device and the brake shoe.
This invention still further provides a drum brake device with an automatic shoe clearance adjustment device, wherein, when an axial force acting on the screw mechanism of the restricting means becomes higher than an urging force of the adjustment spring acting on a pawl end of the adjustment lever, a rotation res
Asai Seiji
Tatsumi Yoshihiro
Butler Douglas C.
Liniak Berenato Longacre & White
Nisshinbo Industries Inc.
LandOfFree
Drum brake device with automatic shoe clearance adjustment... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drum brake device with automatic shoe clearance adjustment..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drum brake device with automatic shoe clearance adjustment... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2585425