JPH03189431A - Squeak prevention device for disc brake - Google Patents

Abstract

PURPOSE:To keep the 2nd-order component of a longitudinal wave resonance frequency over an audible frequency, and make the squeak of a disc brake inaudible by dividing a disc rotor in such a way that the 2nd-order component of the longitudinal wave resonance frequency becomes equal to or above 15kHz. CONSTITUTION:When a longitudinal vibration propagates to a disc rotor 1, the frequency thereof becomes all the more higher if rotor expansion length is smaller, and a disc brake squeak takes place with the 2nd-, 4th- and 6th-order frequency components. The disc rotor 1, therefore, is divided into the predetermined number, and a frequency causing the 2nd-order frequency component is changed to a level equal to or above the upper limit of an audible frequency of 15kHz. The disc rotor 1 is divided, for example, in such a way that two rotors of the same shape having oblong slits 2 dislocated by 180 degrees are arranged at two positions, and the aforesaid oblong slits 2 are formed from the control face part 1a of the rotor 1 to the hub 1b thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a disc brake squeal prevention device that effectively prevents squeal noise generated during braking.

[Prior Art] In a disc brake that performs braking by squeezing a disk-shaped disc rotor that rotates with the axle with friction pads operated by hydraulic pressure, etc., when the disc rotor is pinched by the friction pads, the hardness of the disc rotor decreases. It is known that a very unpleasant high-frequency sound called brake squeal is generated depending on the compatibility between the rotor and the friction pad.

This high-frequency sound occurs when the friction pad used is organic, mainly asbestos.

As shown in FIG. 8, the vibration direction of the disc rotor is the same as the direction of wave propagation, such as the bending vibration or torsional vibration of a plate. It has been confirmed that the wave is mainly based on so-called transverse waves.

That is, FIG. 11 shows the vibration characteristics of the rotor when transverse wave imaging is applied to clarify the resonance point of the rotor regarding transverse waves. -Rikitsutsu 12 Figure is a plot of the frequency and magnitude of the squeal during actual braking in the case of organic bad. As can be seen from FIGS. 11 and 12, it is clear that noise corresponding to the fourth, fifth, and seventh orders of the transverse wave resonance point is generated. As a countermeasure, conventionally, a ring-shaped member made of gold was fitted around the outer periphery of the disc rotor, as described in JP-A-56-164236, or as described in JP-A-54-108880. As shown in Figure 2, there were some models in which holes or grooves were provided in the braking surface of the rotor to shift the resonance point.

[Problems to be solved by the invention] However, with the recent changes in friction materials! ! When semi-metallic and non-asbestos materials began to be used as friction pad materials, conventional vibration damping measures based on transverse waves were unable to produce satisfactory results in suppressing squeal.

Figure 10 shows the frequency and magnitude of the squeal that occurs when braking is actually performed using semi-metallic or non-asbestos friction pads. Frequency in so-called longitudinal wave vibration, where waves propagate in the circumferential direction of the rotor, which is perpendicular to the thickness direction, while causing expansion and contraction vibration in the thickness direction.
It was found that this was extremely similar to the dB characteristic curve diagram (shown in FIG. 9). That is, when comparing both characteristic curve diagrams, 8
．． 4 to 7 (secondary), 12.6 to 7 (fourth), and 17.
6 and (sixth order), a coincidence point where a resonance point exists in both cases was found.

This led to the conclusion that when semi-metallic or non-asbestos friction pads are used, the cause of squeal is due to the longitudinal vibration of the rotor.

Therefore, an object of the present invention is to prevent squealing caused by longitudinal vibration of a disc rotor in a disc brake using a semi-metallic or non-asbestos friction pad.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a disc brake that performs braking by pressing a cementitious or non-asbestos friction pad against the disc rotor. The purpose is to divide the rotor so that the next resonant frequency becomes 15 KHz, which is a high frequency higher than the audio wave frequency.More specifically, X (kaku) is the outer diameter of the disc rotor, and E (dyn/cd) is When Young's modulus of the disc rotor, ρ(g/aj), is the volume density of the disc rotor.

n=4712.4 (0,512X+25.148)
The disc rotor is configured to divide the disc rotor into an integer value obtained by rounding up the decimal point of the value of n obtained by /ajd, or an integer value larger than this integer value.

[Function] When longitudinal wave vibration propagates to the disc rotor, the shorter the rotor development length, the higher the frequency and the brake squeal occurs in the 2nd, 4th, and 6th order. By dividing the sound into a predetermined number of parts, the frequency at which the secondary waves occur is changed to 15, which is the upper limit of the audible frequency that humans can hear, and more than that, so that the squealing sound is virtually inaudible.

[Example] Generally, length Q (am), Young's modulus E (dyn/aJ)
.

The frequency f (Hz) when a longitudinal wave propagates in a rod-shaped solid with a volume density ρ (g/a) is V (am/s)
Let be the speed of sound and λ (am) be the wavelength.

It is known that f=v/λ=pFt/2n (1). (However, p is an integer from order 1 to n of longitudinal waves.)However, in the case of a disc rotor, the shape is circular and there is no open end, so it is slightly different from equation (1) above.
It was experimentally found that the following equation holds true.

f = pi'F7;; / 211 = p stagnation/
2πD... (2) In the case of these two equations, P is an even number of 2.4.6...

Here, D((1 m) is the longitudinal wave propagation diameter, and experiments have revealed that this propagation diameter and the rotor outer diameter X have the relationship shown in FIG. 1.

Based on this formula (2), the outer diameter of the disc rotor of a passenger car commonly used today is X, = 240■ and X, =
Calculating the longitudinal wave resonance frequency of two things in 260th key,
In a rotor with
, = 260m rotor, the secondary wave is 9500Hz, 4
The second wave was 14,5007, and the sixth wave was 19,0007, almost matching the frequency of the actual squeal.

As can be seen from equation (2), there is a relationship in which the frequency f increases as the propagation length πD decreases, so the resonant frequency of the secondary wave is 15KH, which is the upper limit of the human audible frequency.
The propagation length L when exceeding z is calculated as follows: L = p m7/2 f = a7T/ f = p m7 / 15000.

As a result, if the propagation length takes a value of iE/ρ/15000 or less, the frequency will be 15kHz or more, so by dividing the circumferential length πD of the propagation diameter D (b) when the outer diameter of the disc rotor is X, , the developed length of one of the divided pieces) is L
When finding the minimum number of divisions N to achieve the following, N is an integer value obtained by rounding up the decimal point of the value of πD/L. πD/L
If n is n, then n = xD/L= 15000/n (
0,52X425.148)z/10=471
2.4(0,52X+25.148)//1 fuco
It is expressed as

Therefore, the outer diameter X□ actually used by passenger cars is 240
Find the minimum number of divisions that can prevent the squeal of a disc rotor with ■ and outer diameter X□ of 260 mm.

n==1.65 (when xuni 240am), n=1.
77 (when X, = 260-) (However, in this case, Young's modulus E is 12.8
am", and the volume density ρ was set to 7.2 g/cm'.) The minimum division number N was rounded up to 2 for any rotor diameter.

Next, specific means for dividing the disc rotor will be explained based on FIGS. 2 to 7.

In FIG. 2, a long hole 2 is formed extending from the braking surface portion 1a of the disc rotor 1 to the hub portion 1b.

The elongated holes 2 are provided in two locations with the same shape and shifted by 180 degrees.

In Fig. 3, discontinuous elongated holes 3.3' are provided from the outer circumference of the disc rotor 1 toward the hub portion 1b, and the elongated holes 3.3' are shifted by 180 degrees as in Fig. 2. It is located in the same position.

In Fig. 4, two elongated holes 4 are provided in the braking surface portion 1a and the hub portion 1b, and a discontinuous elongated hole 4' is provided at a position shifted by 180 degrees from the outer circumference of the disc rotor 1 toward the hub portion 1b. It is something.

Fig. 5 shows a method of dividing the ventilated rotor 5, in which elongated holes as shown in Figs. 2 to 4 are provided in each of the inner surface 5a and the outer surface 5b. The dividing position may be the same on both sides, or it may be shifted by 90'' as shown in the figure.The width of the elongated hole shown in Figures 2 to 5 varies slightly depending on the size and shape of the disc rotor. It is desirable that it is 4■ or less.

In both cases shown in FIGS. 6 and 7, the disc rotor is completely divided, and then, in the case of FIG. 6, a steel piece 6 is inserted into the divided portion and fixed by caulking or the like.
In the one shown in FIG. 7, the divided portions are connected in a nested structure 7. In the examples shown in Figures 2 to 7, the division is made evenly so that the divided pieces are equal, but the developed length of one divided piece is so long that the resonant frequency of the secondary wave of the longitudinal wave is 15 KHz or more. Any division is fine as long as it is.

[Effect] Taking advantage of the property that when longitudinal waves propagate through an object, the shorter the length of the object, the higher the resonant frequency, the disc rotor is divided and the second-order longitudinal wave that first appears as brake noise is By setting the wave resonance frequency to be higher than the human audible frequency, it is possible to make the squeal sound substantially invisible to humans.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between longitudinal wave propagation diameter and rotor size experimentally determined, and Figs. 2 to 7 show specific examples of dividing the disc rotor of the present invention. Figures 3 and 4 are illustrations of an example in which a regular disc rotor is divided using elongated holes, Figure 5 is an example in which a ventilated rotor is divided, and Figure 6 is after complete division. , Fig. 7 shows an example in which the rotor is completely divided and then connected in a nested structure, Fig. 8 shows the principle of transverse wave vibration, and Fig. 9 shows the frequency when longitudinal wave vibration is applied to the rotor. -dB characteristic curve diagram, Figure 10 is a frequency-dB characteristic curve diagram of the squeal that occurs when actually braking using a semi-metallic or non-asbestos friction pad, and Figure 11 is a diagram of the frequency-dB characteristic curve of the squeal that occurs when a semi-metallic or non-asbestos friction pad is used. FIG. 12 is a frequency-dB characteristic curve diagram of the squeal that occurs when actually braking using an organic pad type friction pad. In the figure, 1... Disc rotor, 2, 3.3I4.4'
...Elongated hole, 5...Ventilated rotor, 6.
...Steel piece, 7...Nested structure.

Claims (6)

[Claims] (1) In disc brakes that perform braking by pressing semi-metallic or non-asbestos friction pads against the disc rotor, it is recommended that the disc rotor be divided so that the longitudinal wave secondary resonance frequency of the disc rotor is 15 KHz or higher. Features anti-squeal device. (2) In a disc brake that performs braking by pressing a semi-metallic or non-asbestos friction pad against the disc rotor, X (mm) is the outer diameter of the disc rotor, and E (dyn/cm^2) is the young diameter of the disc rotor. When p (g/cm^3) is the volume density of the disc rotor, n=4712.4(0.512X+25.148)/√
A squeal prevention device characterized in that a disc rotor is divided by an integer value obtained by rounding up the decimal point of the value of n determined by E/p or an integer value larger than this integer value. (3) The anti-squeal device according to claim 1, characterized in that the disc rotor has elongated holes for division. (4) The anti-squeal device according to claim 3, characterized in that elongated holes are formed in the inner and outer surfaces of the ventilated rotor. (5) The squeal prevention device according to claim 1, wherein the disc rotor is completely divided and then connected with steel pieces. (6) The squeal prevention device according to claim 1, wherein the disc rotor is completely divided and then connected in a nested structure.