Abstract:
In order to prevent squealing of a disk brake, the disk brake has a brake disk with friction rings having locally weakening section moduli which detune corresponding to the natural oscillation mode. As a result, the natural oscillation mode of the brake disk is changed to such an extent that brake squealing is avoided.

Description:
This application claims the priorities of German application Nos. 199 19 437.8, filed Apr. 29, 1999, and 199 42 040.8, filed Sep. 3, 1999, the disclosures of which are expressly incorporated by reference herein. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to an arrangement for preventing the squealing of a disk brake including a particular brake disk, with friction rings, and brake linings. The brake linings have a partial circumference length which relates to an approximately mean circumference of the brake disk. An imposed natural oscillation mode of the brake disk with n-nodes is obtained. Slots are provided in the friction rings. 
     German Patent Document DE 195 07 102 A1 relates to a disk brake which is tuned such that squealing noises during a braking operation are eliminated or reduced by way of adjacent brake linings. This takes place by establishing a certain ratio of the brake lining length to the brake disk circumference. 
     German Patent Document DE 40 41 010 relates to an arrangement for preventing the squealing of a disk brake. In this arrangement, the friction linings, which consist of a semi-metallic or asbestos-free material, are pressed onto a disk rotor or onto a brake disk for carrying out braking. The rotor is divided such that the second order resonance frequency of the longitudinal oscillation of the rotor is larger than 15 kHz. Division of the disk rotor takes place by way of slots which are arranged on the inside and the outside of the rotor. 
     It is an object of the invention to provide a disk brake in which the occurrence of squealing noises is prevented by a detuning of the natural frequency mode of the brake system. 
     According to the invention, this object is achieved by providing the friction rings of the brake disk, in at least one surface area of at least one friction surface thereof, with a local weakening of the section modulus such that a detuning node oscillation which is unequal to a natural vibration mode of the brake disk can be achieved. The nodes are formed from the ratio n=u/L, wherein u is a median brake disk circumference and L is a partial circumference length of the brake linings. Additional advantageous characteristics are also claimed. 
     Principal advantages achieved by the invention include detuning the natural oscillation behavior of existing brakes in the event of a squealing action such that brake squealing is reduced or eliminated. 
     According to the invention, this is essentially achieved by having a local weakening of the section modules “W” in at least one surface area of the friction surfaces of the friction ring of a solid brake disk, or of the friction rings of an internally ventilated brake disk, such that a detuning natural oscillation, which is unlike the natural oscillation mode of the brake disk with the oscillation node “W”, can be achieved. 
     The local weakening or weakenings of the section modulus in one or both friction rings of the brake disk preferably are provided by one or several slots which separate the friction ring or rings and extends or extend from the brake disk center to approximately the outer edge or edges of the friction ring or rings. 
     A resulting detuning of the natural oscillation mode of the brake disk is provided by correspondingly arranged and dimensioned slots in both friction rings or in one friction ring in order to achieve locally reduced section moduli in one or several areas of the friction rings of the brake disk. 
     According to one embodiment of the invention, the slots may be arranged between the cooling ducts of the brake disk as well as on the ribs. Furthermore, the slots may be provided in the outer friction ring as well as in the inner friction ring or in both friction rings. In addition, the slots can also be provided in an alternating sequence in the outer and the inner friction rings. 
     Since each of the slots may separate parts of the friction rings, special links may be required by way of ribs, such as double ribs, which are situated closely side-by-side. When the brake rings have opposed slots, the ribs, which are situated side-by-side, are connected with one another by way of a transverse web. 
     According to the invention, the courses of the slots in the friction rings can be adapted to the courses of the ribs of the cooling ducts so that radial and diagonally extending slots are used which extend on the rib as well as between the ribs. It is also conceivable to arrange slots oppositely diagonally to the ribs and so as to cross over the ribs. 
     If a slot is arranged in the rib of the cooling duct, a wide rib is usually required so that the rib still results in sufficient stiffness. The number of ribs which are wider than the other ribs is selected corresponding to the requirements for preventing brake squealing. Thus, one wider rib or several wider ribs may be required. The width of the slot should be as narrow as possible so that the brake disk is not stressed by unnecessary rubbing effects. For this reason, it is also advantageous for the slot to have chamferings in the friction surface of the brake disk. 
     In every case, a locally reduced section modulus on the brake disk or in the friction rings achieves a detuning of the original natural oscillation mode of the brake disk. The local reduced section modulus achievable by the slots is preferably arranged at the same mutual distance and is designed unequal to the modes of the natural oscillation mode so that, for example, with a six-node oscillation, weakening of the brake disk occurs at four points. 
     Embodiments of the invention are illustrated in the drawings and will be described in detail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of a brake having a brake disk, a friction ring and brake linings; 
     FIG. 2 is a view of an internally ventilated brake disk with a uniform section modulus as seen along the circumference of the brake disk; 
     FIG. 3 is a view of an internally ventilated brake disk with an imposed oscillation mode with n-nodes (six nodes); 
     FIG. 4 is a view of an internally ventilated brake disk with locally reduced section moduli W 1  to Wn at x-points; 
     FIG. 5 is a view of the internally ventilated brake disk according to FIG. 4 with a detuned natural oscillation mode Vs; 
     FIG. 6 is a view of a brake disk with four slots in the internal brake ring; 
     FIG. 7 is a view of a brake disk with four alternating slots in the outer and inner brake rings; 
     FIG. 8 is a view of a brake with opposed slots in the inner and outer brake rings; 
     FIG. 9 is a view of a brake disk with, for example, five slots in the inner brake ring; 
     FIG. 10 is a view of a brake disk with radial partial slots in the inner brake ring; 
     FIG. 11 is a view of a part of the brake disk with a slot in the brake ring on a bent rib of a cooling duct; 
     FIG. 12 is a view of a part of the brake disk with a slot in the brake ring on a radial rib of a cooling duct; 
     FIG. 13 is a view of a diagonally set slot in the brake ring between two diagonally extending or bent ribs of the brake disk; 
     FIG. 14 is a view of a radially extending slot in the brake ring between two radially extending ribs; 
     FIG. 15 is a view of a radially set slot which crosses the radial ribs of the cooling ducts; 
     FIG. 16 is a view of a diagonally set slot which crosses the ribs of cooling ducts extending diagonally in arch shapes; 
     FIG. 17 is a view of an embodiment according to FIGS. 11 or  12  with a slot ending in the rib; 
     FIG. 18 is a view of another embodiment with a slot ending in a double rib; 
     FIG. 19 is a sectional view of the brake disk of FIG. 6 along line A—A; 
     FIG. 20 is a sectional view of the brake disk of FIG. 8 along line B—B; 
     FIG. 21 is a sectional view of a brake disk having a groove in each friction surface of the friction ring; 
     FIG. 22 is a view of another embodiment of a brake disk having an air duct with a hexagonal cross-section; 
     FIG. 23 is a top view of an internally ventilated brake disk with a wide rib having a slot and in which the friction surface is partially cut-open; 
     FIG. 24 is a sectional view of the internally ventilated brake disk in the area of the slot; and 
     FIG. 25 is a sectional view of the friction surface of the internally ventilated brake disk with chamferings of the slot. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A disk brake  1  is schematically illustrated in FIG.  1  and comprises essentially an internally ventilated brake disk  2  with two friction rings  3 ,  4 . The friction rings have friction surfaces R 1  and R 2  on the outsides, which friction surfaces R 1  and R 2  can be acted upon by brake linings  5 ,  6 . These brake linings  5 ,  6  are held in a caliper and can be displaced by way of a brake piston or brake pistons. Between the two friction rings  3 ,  4 , cooling ducts  20  are formed between the ribs  7  which connect the two friction rings  3 ,  4  with one another. In each of FIGS. 2 to  5 , the brake disk  2  is illustrated along the circumference U, so that a natural oscillation mode Es, a detuned oscillation mode Vs, and the locally reduced section moduli W 1  to Wn with the defined oscillations of the brake disk  2  which can be achieved therefrom, can be shown. 
     The natural oscillation form Es of the brake disk  2  is essentially a function of the ratio of the approximately median brake disk circumference U to the brake lining length L. This means that when the brake disk circumference U is, for example, n=6 times as large as the lining length L, a natural oscillation mode Es, also with six nodes K 1  to K 6 , is imposed on the brake disk, as illustrated in detail in FIG.  3 . 
     In the particular case of existing brake systems, and in other cases, the brake disk circumference U as well as the lining length L can no longer be changed. In these cases, so that a significant influence can be achieved with respect to the noise behavior (squealing action), a detuning of the brake system is to be achieved with respect to its original natural oscillation mode Es. 
     A brake system, in the squealing condition, describes a sixnode oscillation (“n=6”). If the noise behavior is to be optimized in such a brake system, optimization takes place by using a brake disk which is changed with respect to the section modulus. On the basis of its construction, this brake disk is forced to carry out a different oscillation mode; that is, the local section moduli “x=W 1  to Wn” (FIG. 4) of the brake disk  2  are unequal to the nodes “n=K 1  to K 6 ” of the natural oscillation mode “Es” of the brake disk  2 . This permits a detuning of the brake system because the section modulus of the brake disk  2  is weakened in a targeted manner, whereby “x” is unequal to “n” in every case. 
     FIG. 5 illustrates the natural oscillation mode Es of a brake disk  2  with a locally reduced section modulus W 1  to Wn. The position of the reduced section modulus W 1  to Wn in the brake or friction rings  3 ,  4  occurs as a result of the selection of the number “x” of the locally weakened section moduli W 1  to Wn (for example, x=4), as in the following. 
     The locally reduced section moduli W 1  to Wn are formed by slots  10  in the first friction ring  3 , the second friction ring  4 , or both of these friction rings. According to one embodiment, the slots  10  separate the brake ring  3  and/or  4  so that, at “x=4”, four partial segments S 1  to S 4  are obtained. 
     FIGS. 6 to  10  illustrate several embodiments having various arrangements of the slots  10 . Locally reduced section moduli “W 1  to Wn” corresponding to the natural oscillations for “Es” and the resulting modes “K” are obtained; such is illustrated, for example, in FIG. 9 by way of five segments S 1  to S 5 . 
     According to FIG. 6, the slots  10  are arranged in the inner friction ring R 1 ; according to FIG. 7, the slots are arranged so as to alternate in the outer and inner friction rings R 2 , R 1 ; and according to FIG. 8, the slots are arranged in both friction rings R 1  and R 2 . 
     Arrangements of the slots  10  similar to those of FIGS. 6 to  8  can also be provided when “x=5” and with five segments S 1  to S 5 . 
     According to another embodiment shown in FIG. 10, the inner friction ring, the outer friction ring, or both the inner and the outer friction rings R 1  and R 2  is or are provided with partial slots  11  which extend from the outer edge  12  radially toward the interior to the center Z and end approximately in the mean circumference U of the brake disk  2 . 
     FIGS. 11 and 12 show that the slots  10  can be arranged directly on the rib  7  of the cooling ducts  20  following their course. FIGS. 13 and 14 show that each slot can be arranged between the ribs  7  of the cooling ducts  20 . 
     According to FIGS. 15 and 16, the slots  10  are set in the brake disk  2  at an angle α, α 1  diagonally to the ribs  7 . According to the invention, the slots  10  can also be arranged corresponding to the embodiment of FIGS. 6 to  10 . 
     In an arrangement of the slot  10  on at least one of the ribs  7  of the brake disk  2 , the rib can either be continuous or end in the center of the rib  7 , as illustrated in detail in FIG.  17 . Such an arrangement of the slots  10  can take place, for example, so as to alternate between the outer and inner friction rings R 2  and R 1 . 
     According to another embodiment of the invention according to FIG. 18, the slot  10  is arranged between two ribs  7   a  and  7   b  which are directly adjacent and form, between one another, a cooling duct  21  additional to the existing cooling ducts  20  between the ribs  7  of the brake disk  2 . 
     In the case of an arrangement of the slots  10  according to FIG. 8 with opposed slots in the friction rings  3  and  4 , the ribs  7  are connected with one another by way of at least one transverse web  15 , as illustrated in detail in FIG.  5 . 
     According to the embodiment of FIG. 21, a reduced local section modulus is achieved by grooves  22  in the friction surfaces R 1  and R 2  in the brake rings which extend from the center Z to the outer edge  12 . 
     Furthermore, the reduced section modulus can also be achieved by at least one cooling duct  24  which is enlarged in its cross-section with respect to the surface in comparison to other cooling ducts  20 . The wall d of the brake ring is smaller in the area of the cooling duct  24  than the wall thickness D in the area of the cooling duct  20 . 
     As illustrated in detail in FIGS. 11 and 12, the slot  10  is arranged approximately in the center of the rib  7 . In this embodiment, the ribs  7  are all of the same width b. So that the slot  10  does not weaken the rib, according to another embodiment of FIGS. 23 to  25 , a rib  7   a  with the measurement b 1  is provided which is wider than the rib  7  and in which the slot  10  is arranged. The slot  10  preferably has a width of &lt;2 mm, particularly of 1.4 mm, the depth t of the slot  10  extending approximately to half the brake disk thickness a. The slot  10  is provided, on both sides of the friction ring surface  30 , with a chamfering  31 ,  32  having a width c and an angle α. The slot  10  may be arranged on the outer friction ring surface and/or on an inner friction ring surface. Five wider ribs  7   a  are preferably provided which are arranged to be uniformly distributed along the circumference. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.