Drum brake
By asymmetrically arranging brake pads and pressure plungers, the NVH problem of commercial vehicle drum brakes has been solved, resulting in reduced noise and vibration, and improved brake stability and comfort.
Patent Information
- Application Number
- CN202480066022.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-11-07
- Filing Date
- 2024-10-21
- Publication Date
- 2026-05-12
AI Technical Summary
Existing commercial vehicle drum brakes exhibit instability in terms of noise, vibration, and acoustic harshness (NVH), primarily due to the force introduction method limiting the circumferential extension of the brake pads and the unit area pressure of the friction material, leading to system vibration and noise problems.
The brake pads and pressure plungers are arranged asymmetrically. The brake pads are radially pressed onto the friction surface of the brake drum by a wedge ring. This ensures that the angular spacing of the pressure plungers is not equal to or does not exceed a ratio of 0.8 and is not lower than 0.6. The brake pads and pressure plungers are arranged in pairs opposite each other to reduce noise caused by the system's inherent modes and servo effects.
It significantly reduces noise generation, avoids micro-relative movement between the brake pads and the anchor housing, improves the NVH characteristics of the system, ensures the stability of the braking process, and reduces perceptible vibration.
Smart Images
Figure CN122029368A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a drum brake as described in the preamble of claim 1. Background Technology
[0002] Drum brakes typically have a roller-shaped rotating component with a friction surface on its inner side (also called a brake drum). Braking force is generated here by pressing the brake pads against the friction surface located on the inner side of the brake drum.
[0003] According to current technology, in drum brakes used in commercial vehicles, the applied operating force is typically enhanced by an S-shaped cam to generate the required braking torque.
[0004] Here, two brake shoes, rotatably supported on one side—with the aid of the eccentric action of an S-shaped cam to amplify the force—are typically pressed against the inner wall of the brake drum. By using two brake shoes, the system is relatively stable in terms of noise generation relative to its inherent modes.
[0005] In the similar drum brakes observed in this paper (where the force transmission is designed such that the force introduced axially along the axis of rotation is enhanced by its deflection, so that the reaction force acts radially on the friction surface of the brake drum), the clamping of the brake pads is achieved by means of a wedge that can move along the axis of rotation.
[0006] The reaction force can be divided by operating multiple pressure plungers.
[0007] In terms of noise generation, the inherent modes of the system are significantly more likely to be encountered in this type of drum brake.
[0008] This is mainly because the force must be applied primarily near the center of the brake pad, thus limiting the possible circumferential extension of the brake pad.
[0009] Therefore, in such systems, at least three brake pads are usually required to prevent the system from being overloaded in terms of unit area pressure and thermal load of the friction material.
[0010] However, due to the large number of force-introducing points, the system is more unstable in generating audible or perceptible vibrations (i.e., the so-called NVH characteristics—noise, vibration, and acoustic roughness). Summary of the Invention
[0011] The objective of this invention is to provide a drum brake of the same type with improved NVH characteristics.
[0012] The proposed task is solved by a drum brake having the features of claim 1.
[0013] The drum brake according to the invention, particularly for commercial vehicles, has a brake drum rotatably supported about a rotation axis.
[0014] The drum brake also has at least two brake pads supported in the receiving space of the brake drum, each brake pad having its own friction pad support and a friction pad disposed on the friction pad support.
[0015] Furthermore, the drum brake has a clamping device mounted on the anchor housing in an anti-rotational manner. This clamping device has a wedge-shaped ring that can move on the cylinder liner of the anchor housing parallel to the rotation axis of the brake drum. By means of the wedge-shaped ring, the brake pads can be pressed radially to the inner surface of the outer shell of the brake drum, which is configured as a friction surface, via their respective pressure plungers.
[0016] The pressure plungers are arranged around the rotation axis of the brake drum such that the first angular distance from the radial motion axis of the first pressure plunger to the radial motion axis of the adjacent second pressure plunger in the circumferential direction is not equal to the second angular distance to the radial motion axis of the adjacent pressure plunger in the opposite circumferential direction.
[0017] The smaller angular spacing (W) in the angular spacing 12 ) and the larger angular spacing (W) in the angular spacing 23 The ratio of ) shall not exceed the limit of 0.8 and shall not be less than the limit of 0.6.
[0018] This applies to the smaller angular spacing in the angular spacing:
[0019] .
[0020] Applicable to larger angular spacings:
[0021] .
[0022] Where N W This refers to the number of pressure plungers or brake pads.
[0023] The asymmetry created by arranging the brake pads in this way within the brake drum avoids the inherent modes of the system, resulting in a significant reduction in noise compared to when the brake pads are evenly distributed.
[0024] Furthermore, this also prevents micro-relative movement between the brake pad backing plate and the anchor housing.
[0025] Advantageous embodiments of the present invention are the technical solutions of the dependent claims.
[0026] According to an advantageous implementation variant, the number of brake pads and pressure plungers is four or six, wherein the pressure plungers are arranged in pairs opposite each other relative to the axis of rotation.
[0027] The forces applied to the brake drum during braking can cancel each other out by the brake pads arranged in pairs opposite each other.
[0028] According to another advantageous implementation variant, the dimensions of the brake pad length viewed in the direction of rotation and the brake pad support height viewed in the radial direction are determined such that the quotient of the length and the support height is greater than or equal to 6 and less than or equal to 22.
[0029] According to an advantageous extension, when the friction radius R of the brake drum is 150 mm ≤ R < 175 mm, the length of the brake pad does not exceed 200 mm; when the friction radius is 175 mm ≤ R < 200 mm, the length of the brake pad does not exceed 240 mm; and when the friction radius is 200 mm ≤ R < 230 mm, the length of the brake pad does not exceed 280 mm.
[0030] According to another advantageous extension, when the friction radius of the brake drum is 150 mm ≤ R < 175 mm and the maximum brake pad length is 200 mm, the quotient of length L and support height H applies:
[0031] ;
[0032] When the friction radius of the brake drum is 175 mm ≤ R < 200 mm and the maximum brake pad length is 240 mm, the quotient of length L and support height H is applicable accordingly:
[0033] ;
[0034] When the friction radius of the brake drum is 200 mm ≤ R < 230 mm and the maximum brake pad length is 280 mm, the quotient of length L and support height applies:
[0035] .
[0036] According to another advantageous implementation variation, the following applies to the brake pad width B as viewed along the axis of rotation in the installed state:
[0037] ,
[0038] Where A Drum It is defined as the free area of the brake drum excluding its flange region. Attached Figure Description
[0039] The preferred embodiments are described in detail below with reference to the accompanying drawings. The drawings are as follows:
[0040] Figure 1 A schematic isometric view of one embodiment of the drum brake according to the invention is shown;
[0041] Figure 2 Show Figure 1 The drum brake shown along Figure 3 A schematic sectional view of the section marked II in the middle;
[0042] Figure 3 Show Figure 1 The drum brake shown along Figure 2 Side view of the section marked III;
[0043] Figure 4 Show Figure 2 The enlarged view of the cross-section shown illustrates the angular spacing between adjacent brake pads; and
[0044] Figure 5 Show Figure 2 Another enlarged view of the cross-sectional view shown is used to illustrate the relative dimensions of the brake pads. Detailed Implementation
[0045] In the following description of the accompanying drawings, terms such as upper, lower, left, right, front, rear, etc., refer only to exemplary illustrations and positions selected for drum brakes, brake drums, brake pads, bearing housings, wedge rings, pressure plungers, etc., in the respective figures. These terms should not be construed as restrictive, meaning that these relationships may vary due to different operating positions or mirror-symmetric designs, etc.
[0046] exist Figure 1 , 2 In Figures 1 and 3, reference numeral 1 generally indicates an embodiment of a drum brake according to the invention, which is particularly suitable for commercial vehicles.
[0047] The drum brake 1 has a brake drum 2 rotatably supported about a rotation axis AR, which is connected to the hub of the wheel axle (not shown) in an anti-rotational manner via an anchor housing 6.
[0048] A plurality of brake pads 3 (four brake pads 3 in the illustrated embodiment) are disposed in the receiving space 22 within the brake drum 2. These brake pads have their own friction pad supports 32 and friction pads 31 disposed on the friction pad supports. The brake pads 3 are positioned with their friction pads 31 facing the inner surface 21 of the outer casing of the brake drum 2, as shown below. Figures 2 to 5 As shown in the example.
[0049] A clamping device is provided on the anchor housing 6. This clamping device has a wedge-shaped ring 5 that can move on the cylinder liner 61 of the anchor housing 6 parallel to the rotation axis AR of the brake drum 2. By means of this wedge-shaped ring, the brake pad 3 can be moved radially to the rotation axis AR of the brake drum 2. Figure 1 The direction r shown is pressed against the inner surface 21 of the outer shell of the brake drum 2, which is a friction surface, as shown. Figure 3 It is clearly visible in the middle.
[0050] In order to transmit the movement of the wedge ring 5 to the brake pad 3, each clamping wedge 33 is provided on the side of the friction pad support 32 opposite to the friction pad 31 as a component of the corresponding brake pad 3. The clamping wedge 33 is connected to the friction pad support 32 via a pressure plunger 34.
[0051] The clamping wedge 33 rests against the clamping surface 51 of the wedge ring 5, as follows: Figure 3 visible.
[0052] The wedge ring 5, for example, can be moved from the non-braking position by the brake piston parallel to the rotation axis AR of the brake drum 2. Figure 3 It moves to the braking position in the z-direction as shown.
[0053] In order to reduce the friction between the pressing surface 51 of the wedge ring 5 and the pressing wedge block 33 of the brake pad 3, a sliding member 4 with multiple rolling elements 41 is provided between the wedge ring 5 and the pressing wedge block 33 of the brake pad 3.
[0054] The number N of brake pads 3 disposed in the receiving space 22 within the brake drum 2 W It depends primarily on the maximum transferable force of the components in the force flow, the size of which is limited by the existing installation space.
[0055] The pressure per unit area on the friction material of the friction lining 31 is determined by the force introduced by each pressure plunger 34 and the available friction surface of each brake lining 3.
[0056] It is particularly preferred that four brake pads 3 be installed in the receiving space 22 inside the brake drum 2.
[0057] Depending on the requirements for the final braking torque, one could also consider two, three, five, six or more brake pads 3.
[0058] The arrangement of the brake pads 3, in terms of the distribution of force on the components in the force flow, is, in principle, most advantageous when uniformly distributed within the brake drum 2. This means an angular division of 4 x 90° = 360° in the case of four pressure plungers 34. However, for NVH characteristics, uniform distribution is always within the inherent modal range and is therefore the worst.
[0059] However, for force transmission components, it is advantageous to choose a uniformly distributed force introduction, because the opposing forces on the support will cancel each other out.
[0060] Therefore, in order to reduce audible or perceptible vibrations and to achieve the most uniform force introduction possible, an even number of pressure plungers 34 or brake pads 3 are preferred, and the pressure plungers 34 or brake pads 3 are arranged in pairs and offset from each other by 180°, but the pressure plungers 34 adjacent to each other have different angles.
[0061] The smaller angular spacing W in the angular spacing 12 The larger angular spacing W in the angular spacing 23 The ratio is chosen such that it does not exceed the limit of 0.8 and is not lower than the limit of 0.6.
[0062] Therefore, in Figure 4 In the embodiment shown with four pressure plungers 34 or four brake pads 3, the radial axial angular distance W between the first pressure plunger 34 and the adjacent second pressure plunger 34 is... 1,2 The radial axial angular distance W between the second pressure plunger 34 and the adjacent third pressure plunger 34 is 75°. 2,3 The angle is 105°. The angular distance between the third and fourth pressure plungers 34 corresponds to the angular distance W. 1,2 Furthermore, the angular distance between the fourth and first pressure plungers 34 corresponds to the angular distance W. 2,3 .
[0063] Therefore, the smaller angular spacing W in the angular spacing 12 The larger angular spacing W in the angular spacing 23 The ratio here is approximately 0.7.
[0064] For the smaller angle spacing (W) in the angle spacing 12 Applicable based on the number of brake pads 3 or pressure plungers 34 installed in the brake drum:
[0065] .
[0066] Correspondingly, for the larger angular spacing (W) in the angular spacing... 23 Applicable based on the number of brake pads 3 or pressure plungers 34 installed in the brake drum:
[0067] .
[0068] In addition to utilizing adjacent angles (angle spacing W) 12 W 23In addition to using the asymmetry of the servo mechanism to avoid resonance caused by the inherent mode, the so-called servo effect also plays a decisive role in suppressing noise generation.
[0069] The servo effect is caused by the opposite radial force vectors of the tangential forces generated on the friction material of the friction pair, namely the friction material of the friction pad 31 of the brake drum 2 and the brake pad 3.
[0070] Because the introduced force acts on the middle region of the brake pad 3, the brake pad 3 is divided into two regions.
[0071] The “facing area” of the brake pad 3 is understood to be an area in which the brake drum 2 first passes through the force-introducing position in the rotational direction and then passes through the contact side of the friction pad 31 of the brake pad 3.
[0072] Conversely, in the "disengagement zone" of the brake pad 3, the brake drum 2 first passes the contact side of the friction pad 31 of the brake pad 3 in its rotational direction and then reaches the force introduction position.
[0073] What is important here is the necessary minimum lever arm H, such as Figure 5 As shown, the lever arm is located between "the part where the back plate 32 of the brake pad 3 abuts against the housing 6" and "the force-introducing surface of the back plate 32 at the interface with the pressure plunger 34".
[0074] Here, the existing support torque is considered as a reaction torque against the torque introduced by the servo effect. When the support torque is large enough, a stable state is achieved.
[0075] If the servo torque is greater than the existing reaction torque, the situation becomes unstable, which causes chattering of the brake pad 3 at the support in the housing 6 on a microscopic scale and thus decisively leads to the generation of unwanted noise.
[0076] Therefore, it is preferable to determine the dimensions of the brake pad length L as viewed along the rotation direction U and the brake pad support height H as viewed along the radial direction r, such that the quotient of the brake pad length L and the support height H is applicable:
[0077] .
[0078] In a preferred embodiment, when the friction radius R of the brake drum 2 is 150 mm ≤ R < 175 mm, the maximum length L of the brake pad is 200 mm.
[0079] When the friction radius R of the brake drum 2 is 175 mm ≤ R < 200 mm, the brake pad length L is preferably 240 mm at most, and when the friction radius R of the brake drum 2 is 200 mm ≤ R < 230 mm, the brake pad length L is preferably no more than 280 mm.
[0080] Particularly preferred when the friction radius R of the brake drum 2 is 150 mm ≤ R < 175 mm and the maximum brake pad length L is 200 mm, the quotient of brake pad length (L) and support height (H) is applicable:
[0081] .
[0082] When the friction radius R of the brake drum 2 is 175 mm ≤ R < 200 mm and the maximum brake pad length L is 240 mm, the preferred ratio of brake pad length (L) to support height (H) is as follows:
[0083] .
[0084] When the friction radius R of the brake drum 2 is 200 mm ≤ R < 230 mm and the maximum length L of the brake pad is 280 mm, the preferred ratio of length (L) to support height (H) is:
[0085] .
[0086] The following description will use the width B of the brake pad 3 to illustrate its extension dimension parallel to the rotation axis AR of the brake drum 2.
[0087] "Area coverage ratio" can be understood as the percentage of the friction surface of the brake drum that is covered by the surface of the friction material of the brake lining.
[0088] Since the purpose of the force transmission method described above is to transfer the advantages of disc brakes in terms of friction pairs to the principle of drum brakes, the ratio in disc brakes is used as the comparison value for the design described herein.
[0089] In disc brakes used in commercial vehicles, there is an area coverage ratio of approximately 16%. Typically, this considers the pure friction surface of the rotating component. Unlike disc brake pads which are in contact with each other on both sides, drum brakes experience pressure on only one side of the friction surface, therefore a larger area of the rotating component must be considered. Similarly, in similar applications, brake drums operate at a lower temperature level than brake discs due to the larger surface area available for heat dissipation. For this reason, a slightly higher area coverage ratio of 20% is determined.
[0090] It should be noted that, based on the given application space, the free area of brake drum 2 is approximately constant and is only slightly affected by the varying brake pad width B. The free area A of brake drum 2 Drum This refers to the area of brake drum 2 minus the area of flange region 23.
[0091] The following is preferably applicable for the brake pad width (B) as viewed along the axis of rotation (AR) in the installed state:
[0092] .
[0093] For example, with a friction diameter R of 213.5 mm and a brake pad quantity N... W There are 4 brake pads, the length L of which is 200 mm, and the free area A of the brake drum 2. Drum With a diameter of 6760 cm², the maximum permissible brake pad width B is therefore 162 mm.
[0094] It should be noted that the maximum permissible width B varies with the free area A of the brake drum 2. Drum It increases with the increase of the brake pad length (L) and decreases with the increase of the brake pad length (L).
[0095] List of reference numerals
[0096] 1. Drum brake
[0097] 2 Brake Drums
[0098] 21 Inner surface of the outer casing
[0099] 22 storage space
[0100] 23 Flange Area
[0101] 3 Brake pads
[0102] 31 Friction Liner
[0103] 32 Friction Liner Support
[0104] 33 clamping wedge block
[0105] 34 pressure plunger
[0106] 4 sliding parts
[0107] 41 Rolling element
[0108] 5 wedge rings
[0109] 51 Compacting surface
[0110] 52 Support Surface
[0111] 53 End Stop
[0112] 54 inner weeks
[0113] 55 lateral concave
[0114] 6 Anchored Shell
[0115] 61 cylinder liner
[0116] 62 Liner Receiving Section
[0117] AR Rotation Axis
[0118] U-shaped brake drum circumferential direction
[0119] R brake drum friction radius
[0120] r direction
[0121] z direction
[0122] T r1 radial axis
[0123] T r2 radial axis
[0124] T r3 radial axis
[0125] N W Number of brake pads
[0126] L Brake pad length
[0127] B Brake pad width
[0128] H support height
Claims
1. A drum brake (1) for commercial vehicles, comprising: Brake drum (2) is rotatably supported about the axis of rotation (AR). Quantity (N) W The brake pads (3) are at least two brake pads (3) supported in the receiving space (22) of the brake drum (2), and these brake pads have their own friction pad supports (32) and friction pads (31) disposed on the friction pad supports. A clamping device is provided on the anchor housing (6) in an anti-rotational manner. This clamping device has a wedge ring (5) that can move on the cylinder liner (61) of the anchor housing (6) parallel to the rotation axis (AR) of the brake drum (2). By means of the wedge ring, the brake pads (3) can be pressed radially to the rotation axis (AR) of the brake drum (2) via their respective pressure plungers (34) onto the inner surface (21) of the outer shell of the brake drum (2), which is constructed as a friction surface. Its features are, The pressure plunger (34) is arranged about the rotation axis (AR) of the brake drum (2) such that the radial axis (T) of the first pressure plunger (34) among the pressure plungers is perpendicular to the radial axis (T). r2 ) originating from the radial axis (T) of the adjacent second pressure plunger (34) in the circumferential direction (U). r1 The first angular spacing (W) 12 ) is not equal to the radial axis (T) of the pressure plunger (34) adjacent to the circumferential direction (U). r3 The second angular spacing (W) 23 ), The smaller angle spacing (W) in the angle spacing 12 ) and the larger of the angular spacings (W) 23 The ratio of ( ) to the limit shall not exceed 0.8 and shall not be lower than the limit of 0.
6. And for the smaller angular spacing (W) in the angular spacing 12 Applicable to: And for the larger angular spacing (W) in the angular spacing 23 Applicable to: 。 2. The drum brake (1) according to claim 1, characterized in that, The number (N) of the brake pads (3) and pressure plungers (34) W There are four or six, wherein the pressure plungers (34) are arranged in pairs opposite each other relative to the axis of rotation (AR).
3. The drum brake (1) according to claim 1 or 2, characterized in that, The dimensions of the brake pad (3), the length (L) of the brake pad as viewed in the direction of rotation and the support height (H) as viewed in the radial direction, are determined such that the quotient of the length (L) and the support height (H) is applicable: 。 4. The drum brake (1) according to claim 3, characterized in that, When the friction radius (R) of the brake drum (2) is 150 mm ≤ R < 175 mm, the length (L) of the brake pads shall not exceed 200 mm; when the friction radius (R) of the brake drum (2) is 175 mm ≤ R < 200 mm, the length (L) of the brake pads shall not exceed 240 mm; and when the friction radius (R) of the brake drum (2) is 200 mm ≤ R < 230 mm, the length (L) of the brake pads shall not exceed 280 mm.
5. The drum brake (1) according to claim 4, characterized in that, a) When the friction radius (R) of the brake drum (2) is 150 mm ≤ R < 175 mm and the maximum brake pad length (L) is 200 mm, the quotient of length (L) and support height (H) applies: ； b) When the friction radius (R) of the brake drum (2) is 175 mm ≤ R < 200 mm and the maximum brake pad length (L) is 240 mm, the quotient of length (L) and support height (H) applies: ； c) And when the friction radius (R) of the brake drum (2) is 200 mm ≤ R < 230 mm and the maximum brake pad length (L) is 280 mm, the quotient of length (L) and support height (H) applies: 。 6. The brake drum (1) according to any one of the preceding claims, characterized in that, Applicable to the brake pad width (B) as viewed along the axis of rotation (AR) in the installed state: ， Where A Drum The free area of the brake drum (2) excluding its flange region (23) is defined as the area of the brake drum (2).