JPH017875Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention This invention relates to an automatic clearance adjustment device for wheel cylinders that is configured to automatically adjust the clearance between the inner peripheral surface of the drum and the pad only at room temperature. be.

Conventional technology A conventional automatic clearance adjustment device between the inner peripheral surface of the drum and the pad in a wheel cylinder is capable of adjusting the gap between the inner peripheral surface of the drum and the pad, regardless of the drum temperature or the temperature of the hydraulic oil in the wheel cylinder. When a gap above a certain value occurs, it is automatically activated as the wheel cylinder operates, and the gap between the inner peripheral surface of the drum and the pad is reduced to a gap of a certain value. has been done.

Problems to be Solved Therefore, in the conventional automatic gap adjustment device, the gap between the inner peripheral surface of the drum and the pad is adjusted while the temperature of the hydraulic oil in the drum or wheel cylinder is in the high temperature range. In the so-called room temperature range, the gap is less than a certain value, and there is a problem in that the inner peripheral surface of the drum and the pad are in contact even when not braking, causing a so-called dragging phenomenon.

The object of this invention is to provide a new automatic gap adjustment device for a wheel cylinder that is configured to adjust the gap only in the room temperature range and solves the above-mentioned problems.

Means for Solving the Constituent Problems of the Invention In order to solve the above-mentioned problems, this invention has a brake shoe web that comes into contact with one end edge of the brake shoe web.
A shoe engagement tool made of temperature-sensitive metal is provided on the head of the adjustment bolt of the wheel cylinder, and the shoe web is clamped with the shoe engagement tool to connect the wheel cylinder and brake shoe. It is.

Function Adjustment of the gap between the inner circumferential surface of the drum and the pad is achieved by meshing with a cylindrical fixed guide fixed to the inner circumferential surface of the wheel cylinder, which rotates and moves in the axial direction as the piston moves. with a guide who
This is achieved by the progress of engagement of the ratchet teeth on the engagement surface of the clutch, which engages with the guide and is fixed to the end surface of the piston.
As the guide continues to rotate, the ratchet tooth profile of the guide exceeds the ratchet tooth profile of the clutch that is currently engaged, creating a new meshing condition, but the piston rotates by a central angle corresponding to the difference between the new and old meshing conditions. . However, since the adjustment bolt that threadably fits into the piston is connected to the shoe through the shoe engagement tool, it does not rotate and is pushed out by a pitch corresponding to the center angle, causing the pad and drum inner circumferential surface to Reduce the gap between. In this case, the shew engaging tool tightly clamps the shew web at room temperature, but when the temperature exceeds a certain level, the part that clamps the shew web opens, creating a gap between the shew web and the guide element. Even as the rotation progresses, only the center angle corresponding to the gap between the shoe engagement tool and the shoe web remains.
The piston and adjustment bolt rotate, making it difficult to form a new meshing tooth profile between the guide and the clutch. In other words, when the temperature exceeds a certain level, the automatic clearance adjustment device for the wheel cylinder does not operate.

Example The illustrated embodiment will be described below.

1 is a wheel cylinder. In the illustrated embodiment, a double-acting type is shown, and the components installed in the wheel cylinder 1 are arranged symmetrically with respect to the central cross section. When a single-acting wheel cylinder 1 is used, it is formed of components that are mounted on either the left or right side. A fixed guide element 2 formed into a thick-walled cylinder is press-fitted into the inner peripheral surface of the wheel cylinder 1 at the center in the axial direction. A pressure introduction hole 3 is provided. A helical tooth profile 4 is formed on the inner peripheral surface of the fixed guide 2, and a helical tooth profile 4 is formed on the outer peripheral surface of the guide 5, which is formed in the shape of a ring with a boss.
It meshes with helical gear 6. Further, the guide 5 has a pawl tooth shape 7 formed on the end face of the boss, and one ring end face of the clutch 8 formed in a ring shape is formed as a pawl wheel 9 to form a ratchet engagement. The clutch 8 is press-fitted into a clutch base 11 that protrudes from the center of the inner end surface of the piston 10, and is formed to move integrally with the piston 10. Further, the clutch base 11 is provided with a bottom outer surface of a spring holder 12 formed in a cylindrical shape with a flange and a bottom, which is screwed and fixed in a state where it is in contact with the end surface of the clutch base 11. A coil spring 13 is sandwiched between the ring-shaped end surfaces of the guide element 5 and the guide element 5, and is configured to constantly press the ratchet engagement surfaces of the guide element 5 and the clutch 8 with an appropriate pressing force. Further, the piston 10 is formed with a screw hole 14 opening at the center of the outer end surface, into which an adjustment bolt 15 is screwed. Adjustment bolt 15
A parallel bottomed groove 17 is formed in the head 16. The groove width of the parallel bottomed groove 17 is formed to be larger than the plate thickness of the web 19 of the brake shoe 18, and the shoe engaging tool 20 is inserted into the parallel bottomed groove 17. The web 19 is fitted into the parallel bottomed groove 17 through the parallel bottomed groove 17, and the outer peripheral edge of the web 19 is formed so as to contact the bottom surface of the parallel bottomed groove 17. The shoe engagement tool 20 includes a clamping portion 21 formed by curving opposing surfaces at the opening edge so as to have an inwardly convex surface.
and an engaging portion 22 which is connected to the clamping portion 21 and is curved so that the opposing inner surface has an outwardly convex surface.
are connected to each other by a bottom part 23 formed of an arcuate curved surface so as to have a slightly convex surface in the outward direction, and the bottom part 23 is brought into contact with the bottom of the parallel bottomed groove 17, and a pair is formed facing each other. The engaging portion 22 formed by the parallel bottomed groove 1
The shoe 18 is press-fitted between the parallel walls of the shoe 18, and the web 19 of the shoe 18 is sandwiched between the clamping portions 21. The shoe engagement tool 20 is formed to have the same length as the parallel bottomed groove 17, and has a high expansion material such as Monel metal on the inside and a low expansion material such as 40% nickel steel on the outside. It is formed from a bimetal bonded together. In this automatic gap adjustment device, as the gap between the inner peripheral surface of the drum and the pad increases and the amount of displacement of the shoe 18 during brake operation increases, the amount of protrusion (forward stroke) of the piston 10 increases. As the amount of protrusion of the piston 10 increases, the rotation angle of the guide element 5 increases, and the guide element 5 passes over the peak of the pawl wheel 9 of the clutch 8 that is currently engaged.
Form a new ratchet mesh. In other words, the adjustment bolt 15 holds the web 19 of the shoe 18 with the clamping part 21 of the shoe engagement tool 20, and the threaded surface of the adjustment bolt 15 that is screwed into the screw hole 14 of the piston 10 is under surface pressure during braking. is high, so clutch 8
does not rotate, and the guide element 5 is connected to the coil spring 13.
Overcoming the pressing force, it rotates and forms a new ratchet engagement. If the pressure is removed in this state, the screw hole 14 and the threaded portion of the adjustment bolt 15 will slip by a center angle corresponding to one peak of the pawl wheel 9 of the clutch 8, and the adjustment bolt will slip by a pitch corresponding to this center angle. 15 stands out and reduces the gap. In this case, when the pressure is removed, the shoe 18 is formed to be pulled back by the tension of a separately provided return spring. When the drum temperature rises above a certain temperature, the clamping portion 21 of the shoe engagement tool 20 that is engaged with the parallel bottomed groove 17 of the adjustment bolt 15 opens outward, and the shoe 18 that is being clamped opens outward. A gap is created between the web 19 and the web 19. Play occurs in the rotational direction by a central angle corresponding to this gap, and as the guide 5 rotates, the piston 2 rotates, and the pawl tooth profile 7 does not exceed the peak of the pawl wheel 9 of the clutch 8, maintaining the current meshing state. maintained and restored as the piston 10 is depressurized.

Effects This invention is constructed as claimed in the utility model registration based on the above-mentioned embodiment, so that in the normal temperature range, the web of the brake shoe and the adjustment bolt are tightly held by the shoe engagement tool. Therefore, there is no play in the rotation angle, and the gap between the inner peripheral surface of the drum and the pad can be adjusted with high precision. In addition, when the temperature rises above a certain value, the gap between the clamping parts of the shoe engagement tool opens, and play occurs between the web and the plate thickness, and the rotor does not go beyond the ratchet tooth profile of the clutch, making it impossible to adjust the clearance. can do. As a result, there is no risk of over-adjustment problems caused by thermal expansion, and the reference gap between the inner circumferential surface of the drum and the pad can be determined with high precision at room temperature, making it possible to perform brake adjustment work efficiently. .

[Brief explanation of the drawing]

Figure 1 is a sectional view with a part of the brake device removed, Figure 2 is an enlarged sectional view of the adjustment bolt head, and Figure 3 is an enlarged sectional view of the adjustment bolt head.
The figure is a plan view thereof. 1... Wheel cylinder, 2... Fixed guide, 5... Guide, 8... Clutch, 10... Piston, 15... Adjustment bolt, 16... Head, 1
7... Parallel bottomed groove, 18... Brake shoe, 1
9... web, 20... shoe engagement tool, 21...
Clamping part, 22... Engagement part, 23... Bottom part.

Claims (1)

[Scope of utility model registration request] Through the ratchet engagement of the guide, which moves and rotates as the piston moves within the wheel cylinder, and the clutch, which rotates together with the piston,
In an automatic gap adjustment device that adjusts the gap by rotating a piston, screwing it into the piston, and protruding an adjustment bolt that engages with the brake shoe, the screw fits into the screw hole 14 in the center of the outer end surface of the piston 10. A parallel bottomed groove 17 formed in the head 16 of the adjustment bolt 15 is provided with a clamping part 21 that clamps the web 19 of the shoe 18 and an engaging part 22 that engages with the parallel walls of the parallel bottomed groove 17. The inner walls of the clamping part 21 and the engaging part 22 are made of a high-expansion metal, and the outer walls are made of a bimetal made of a low-expansion metal. An automatic clearance adjustment device for a wheel cylinder, characterized in that a shoe engagement tool 20 is provided, which opens and reduces the clamping interval of the clamping parts 21 as the temperature decreases.