Patent Application
20100025166
This invention relates to a caliper brake device for a vehicle, which applies a brake to a rotary body by sandwiching two frictional surfaces formed on either side face of the rotary body.
A railway vehicle is typically installed with a pneumatic-hydraulic converter that converts air pressure supplied from an air pressure source into oil pressure such that a hydraulic brake is activated by the oil pressure, which is supplied thereto from the pneumatic-hydraulic converter via a hydraulic pipe.
In relation to this point, JPH08-226469 and JPH08-226471, published by the Japan Patent Office in 1996, disclose a hydraulic brake device for a railway vehicle in which a hydraulic cylinder presses a brake pad against a frictional surface of a rotary body such as a brake rotor in accordance with a supplied oil pressure.
Meanwhile, by installing an air pressure brake that is activated by air pressure supplied from the air pressure source in the railway vehicle, it may be possible to omit the pneumatic-hydraulic converter and the hydraulic pipe.
In relation to this point, JPH11-193835, published by the Japan Patent Office in 1999, discloses an air brake device for a railway vehicle in which an air pressure actuator presses a brake pad against a frictional surface of a rotary body when compressed air is supplied to an air chamber of the air pressure actuator.
In these railway vehicle brake devices, the hydraulic cylinder or the actuator presses a part of the brake pad rather than pressing the entire brake pad. As a result, a brake caliper may be bent by a reaction force corresponding to the pressing force such that contact with the frictional surface cannot be secured reliably. Further, when a local temperature increase occurs in the brake pad or a frictional coefficient of the brake pad decreases, it may be impossible for the brake pad to exhibit its original braking force. As a result, partial wear is likely to occur on the brake pad.
In the case of an air brake employing a lever, it is difficult to cause the brake pad to press the frictional surface evenly due to the effect of frictional force acting on a bearing portion of the lever, and therefore partial wear is particularly likely to occur on the brake pad.
It is therefore an object of this invention to make a pressing force with which a brake pad presses a rotary body even.
To achieve the object described above, this invention provides a caliper brake device for a vehicle, which applies a brake to rotation of a rotary body by sandwiching a pair of frictional surfaces formed on either side of the rotary body, comprising a brake caliper that is fixed to a vehicle body and comprises a pair of caliper arms disposed so as to straddle the rotary body, a brake pad that is supported on each of the caliper arms so as to face the respective frictional surfaces, and applies a braking force to the respective frictional surfaces by displacing toward the respective frictional surfaces, a pressure chamber formed in each of the caliper arms, a diaphragm that expands in accordance with a pressure of the pressure chamber, a plurality of pistons that drive the brake pad toward the corresponding frictional surface in accordance with the expansion of the diaphragm, and a guide member that guides a displacement of the plurality of pistons in a right-angle direction relative to the corresponding frictional surface.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
Referring to
The pair of brake pads 7 are supported respectively on tip ends of a pair of caliper arms 12. The pair of caliper arms 12 are formed as a two-pronged fork extending from a yoke 13 of a brake caliper 10 so as to straddle the vehicle wheel 5. The brake caliper 10 comprises a flange portion 20. The flange portion 20 is fixed to a bogie of the railway vehicle via a bolt.
The brake caliper 10 has a symmetrical shape relative to a center line Ozx shown in
Referring to
The brake pads 7 are supported on the respective caliper arms 12 via the actuators 60 to be capable of displacing in the X axis direction.
Referring to
Referring to
To attach the brake pad 7 to the caliper arm 12, the engaging portion 91 of the brake pad 7 is inserted into an inner side of the guide rail 8a of the holder 8 from below in a state where the adjustor 41 and the anchor pin 43 are detached from the lower end of the caliper arm 12. When the engaging portion 91 has reached a predetermined position of the holder 8, the adjustor 41 and the anchor pin 43 are fixed to the lower end of the caliper arm 12 by the anchor bolt 42. Thus, the upper end and lower end of the holder 8 are respectively fitted into the engaging grooves 98 of the anchor pins 43 such that displacement of the brake pad 7 in the Y axis direction is restricted.
The adjustor 41 comprises a return spring 44 that biases the brake pad 7 in a separating direction from the frictional surface 6, and a gap adjustment mechanism 45 that adjusts a gap between the brake pad 7 and the frictional surface 6 to a substantially fixed value when a force other than the spring force of the return spring 44 does not act on the brake pad 7. When the brake is disengaged, the brake pad 7 is removed from the frictional surface 6 by the return spring 44 and opposes the frictional surface 6 at the gap prescribed by the gap adjustment mechanism 45.
The adjustor 41 is a well-known mechanism disclosed in JPH06-288417, published by the Japan Patent Office in 1994. The content thereof is incorporated herein by reference, and therefore a detailed description has been omitted.
By means of the support structure described above, the brake pad 7 is supported by the caliper arm 12 to be capable of displacing in the X axis direction while remaining parallel to the frictional surface 6.
Referring to
Returning to
A pressure chamber 63 is formed between the diaphragm 75 and the cover 92 in the inside of the cylinder 80. The pressure chamber 63 is caused to expand by compressed air supplied from the outside, and the diaphragm 75 presses the brake pad 7 in the X axis direction via the pistons 55 and the holder 8 such that the brake pad 7 is pressed against the frictional surface 6. For this purpose, the holder 8 is formed in advance with a larger planar form than a region of the diaphragm 75 in which the pistons 55 are disposed.
The cylinder 80 comprises a cylinder inner wall 82 that has a substantially elliptical cross-section and extends in the X axis direction, the cover 92, which closes one end of the cylinder 80 to form a bottom portion, and a ring-shaped attachment seat 81 having a substantially elliptical outer form for latching a peripheral edge portion 76 of the diaphragm 75 to a peripheral edge portion of the cover 92. The attachment seat 81 is formed on a plane defined by the Y axis and the Z axis.
Returning to
The lining 9 of the brake pad 7 takes an overall curved shape in a rotation direction of the vehicle wheel 5, and is divided into a plurality of segments relative to the rotation direction of the vehicle wheel 5, as shown by broken lines in the figure. Each segment is fixed to the body 97 shown in
The cylinder inner wall 82 is constituted by curved front and rear curved wall portions 82c and 82d, and upper and lower arc-shaped wall portions 82a and 82b connected to the front and rear curved wall portions 82c and 82d. The pressure chamber 63 having a substantially elliptical cross-section, which is delimited by these wall surfaces, has a larger sectional area than the lining 9 of the brake pad 7.
Returning to
The peripheral edge portion 76 of the diaphragm 75 is sandwiched between the attachment seat 81 and the cover 92. A chamfered portion 83 is formed between the attachment seat 81 and the cylinder inner wall 82 of the cylinder 80. The chamfered portion 83 serves to ensure that the diaphragm 75 curves gently, rather than sharply, from the peripheral edge portion 76 to the bellows portion 77.
A compound material formed by combining a reinforcing material such as carbon fiber or Kevler fiber, for example, with a resinous elastic material may be used as the material of the diaphragm 75. Alternatively, the diaphragm 75 may be constituted by a thin metal plate.
An attachment seat 95 opposing the vehicle wheel 5 is formed on an opposite end portion of the cylinder 80 to the cover 92. The guide frame 65 is fastened to the attachment seat 95 via a plurality of bolts 96. The guide frame 65 may be formed integrally with the brake caliper 10 in advance.
The plurality of pistons 55 respectively penetrate guide holes 65a formed in the guide frame 65 to be free to slide, and are interposed between the piston pressing portion 79 of the diaphragm 75 and the holder 8. A disc-shaped adiabatic plate 61 formed from an adiabatic material is attached to a contact surface of the piston 55 that contacts the holder 8. Instead of employing the adiabatic plate 61, processing such as adiabatic material spraying may be implemented on the piston 55 to improve the heat insulation performance of the piston 55.
Returning to
An outer diameter of each piston 55 is set at 22 millimeters (mm), for example. The pistons 55 are disposed at a substantially equal density over the entire region of the brake pad 7.
Here, the pistons 55 are disposed in three columns, but the arrangement of the pistons 55 is not limited thereto. By varying the outer diameter and axial direction length of the pistons 55, a distribution of the pressing force applied to the brake pad 7 can be controlled.
A through hole 69 for supplying compressed air to the pressure chamber 63 from an air pressure source installed in the railway vehicle is formed in the brake caliper 10. The through hole 69 is formed on the center line Ozy of the brake caliper 10 by mechanical processing. The supply of compressed air into the pressure chamber 63 through the through hole 69 is controlled via a switching valve that operates in accordance with a command signal from a controller. When braking is not underway, the pressure chamber 63 is open to the atmosphere.
In the caliper brake device 1, the brake pad 7 and actuator 60 constituted as described above are provided on the respective tip ends of the pair of caliper arms 12.
When braking is not underway in the caliper brake device 1, the brake pads 7 are removed from the frictional surfaces 6 of the vehicle wheel 5 by the elastic force of the return springs 44 of the pair of adjustors 41 in the respective caliper arms 12. Furthermore, the pressure in the pressure chamber 63 is low, and therefore the diaphragm 75 contracts such that the pistons 55 are held in a withdrawn position.
During braking, the diaphragm 75 expands in accordance with the supply of compressed air to the pressure chamber 63 in the respective caliper arms 12. Thus, as shown in
Diameter of cylinder 47: Π 38 (mm)×2
Sectional area of cylinder 47 (pressure receiving surface area of piston): 2,268 square millimeters (mm2)
Required oil pressure: 9 megapascals (MPa)
Pressing force=2268×9=approx. 20 kilonewtons (kN)
Sectional area of cylinder 80 (=pressure receiving surface area of diaphragm 75): 27,697 (mm2)
Required air pressure: 0.75 (MPa)
Pressing force=27697×0.75=approx. 20 (kN)
The brake pad pressing force of the caliper brake device 1 according to this invention is approximately 20 kN, i.e. identical to that of the conventional hydraulic piston type caliper brake device.
Hence, the diaphragm 75 has a sufficiently large pressure receiving surface area within the limited space of the brake caliper 10, and therefore the actuator 60 of the caliper brake device 1 can apply the required pressing force to the brake pad 7 using air pressure that is much lower than the required oil pressure.
The caliper brake device 1 according to this invention presses the brake pad 7 against the frictional surface 6 via the plurality of pistons 55 by causing the diaphragm 75 to expand. Even when the brake caliper 10 bends or deformation occurs on a rotation surface of the frictional surface due to a reaction force to the pressing force, the brake pad 7 is pressed against the frictional surface 6 with an even contact pressure. Therefore, a frictional coefficient of the brake pad 7 can be kept high at all times, and as a result, the original braking force of the brake pad 7 can be exhibited. Furthermore, since the contact pressure is even, local temperature increases are unlikely to occur in the brake pad 7 or the frictional surface, and therefore partial wear is unlikely to occur on the brake pad 7 and the frictional surface 6.
When the caliper arm 12 of the brake caliper 10 bends in a separating direction from the frictional surface 6 of the vehicle wheel 5 during braking, the pistons 55 perform a large stroke in a region where the separation distance between the caliper arm 12 and the frictional surface 6 is large, and therefore the brake pad 7 is held parallel to the frictional surface 6. Hence, partial wear of the lining 9 in a radial direction can be prevented.
In the caliper brake device 1, the pistons 55 and the guide frame 65 are interposed between the diaphragm 75 and the brake pad 7, and therefore heat generated by the brake pad 7 is prevented from being transmitted to the diaphragm 75 by these members. Hence, the diaphragm 75 is unlikely to suffer heat-related damage.
The actuator 60 drives the brake pad 7 directly using air pressure supplied from the air pressure source installed in the railway vehicle, and therefore, there is no need to install a pneumatic-hydraulic converter, an oil pressure source, and hydraulic piping in the railway vehicle. Hence, by employing the caliper brake device 1 according to this invention, a reduction in the weight of the railway vehicle can be achieved.
Instead of supplying air pressure to the pressure chamber 63 of the caliper brake device 1, oil pressure may be supplied. In this case also, a large number of pistons are used in comparison with a conventional hydraulic piston type caliper brake device, and therefore the brake pad 7 can be pressed evenly. Moreover, by employing a large number of pistons, the pressure receiving surface area increases, and as a result, the required pressing force can be secured at a low oil pressure. Hence, the size of the pneumatic-hydraulic converter can be reduced.
In the caliper brake device 1, the pressure chamber 63 is disposed between the pair of anchor pins 43, and the cylinder inner wall 82 that delimits the pressure chamber 63 is formed with a substantially elliptical cross-section. Therefore, a sufficiently large pressure receiving surface area can be secured on the diaphragm 75, and the pressing force can be applied to a wide range of the brake pad 7. Furthermore, the diaphragm 75 housed in the pressure chamber 63 having a substantially elliptical cross-section curves gently in a circumferential direction, or in other words in a ZY plane, and does not have any sites that curve sharply. Moreover, the chamfered portion 83 formed between the attachment seat 81 and the cylinder inner wall 82 mitigates the sharp curve of the diaphragm 75 in an XY plane. Hence, load concentration is unlikely to occur in the diaphragm 75, and as a result, the diaphragm 75 exhibits favorable durability.
In the actuator 60, the bellows portion 77 is disposed on the inside of the cylinder inner wall 82, and therefore a situation in which the bellows portion 77 is caused to expand sideward by the air pressure introduced into the pressure chamber 63 during braking can be prevented by the cylinder inner wall 82. Hence, an air flow rate required to press the brake pad 7 can be suppressed to a low level, and the response of the vehicle wheel 5 to braking by the brake pad 7 can be improved.
The peripheral edge portion 76 of the diaphragm 75 is sandwiched between the ring-shaped attachment seat 81 and the cover 92, and the pressure chamber 63 is provided between the cover 92 and the diaphragm 75. Therefore, the actuator 60 can be accommodated within a small space inside the brake caliper 10 such that an increase in the size of the brake caliper 10 is avoided.
Further, the pistons 55 contact the holder 8 via the adiabatic plate 61, and therefore the heat of the brake pad 7 is unlikely to be transmitted to the diaphragm 75. Thus, an environment in which the diaphragm 75 is unlikely to suffer heat damage is obtained.
In the caliper brake device 1, the plurality of pistons 55 press the brake pad 7 via the holder 8 latched to the anchor pins 43. This structure is preferable in terms of improving the support rigidity of the brake pad 7. Moreover, the brake pad 7 can be attached to and detached from the brake caliper 10 easily.
Referring to
In this embodiment, the holder 8 is omitted and the brake pad 7 is supported by the anchor pins 43 directly.
The brake pad 7 is constituted by the lining 9 and the body 97 to which the lining 9 is fixed.
A ring-shaped groove 86 is formed in the tip end of each anchor pin 43. An engaging portion 85 that engages with the ring-shaped groove 86 is formed on the upper end and the lower end of the body 97.
The brake pad 7 engages the engaging portion 85 on the upper end of the body 97 with the ring-shaped groove 86 in the upper anchor pin 43 and engages the engaging portion 85 on the lower end of the body 97 with the ring-shaped groove 86 in the lower anchor pin 43. Thus, the brake pad 7 is supported on the caliper arm 12 to be capable of advancing and retreating relative to the frictional surface 6, and therefore the brake pad 7 advances and retreats relative to the frictional surface 6 in accordance with expansion and contraction of the diaphragm 75.
All other structures of the caliper brake device 1 are identical to their counterparts in the first embodiment.
In this embodiment, the holder 8 is omitted and the two ends of the brake pad 7 are latched directly to the anchor pins 43, and therefore the structure of the caliper brake device 1 can be simplified. Further, the dimension of the brake caliper 10 in the X axis direction can be reduced. By omitting the holder 8, the ability of the lining 9 to follow the shape and deformation of the frictional surface 6 is improved.
Referring to
In this embodiment, the support structure of the diaphragm 75 differs from that of the second embodiment.
The caliper brake device 1 according to this embodiment includes a cylinder 70 instead of the cylinder 80 according to the first embodiment.
The cylinder 70 comprises a cylinder inner wall 71 extending in the X axis direction, a bottom portion 72 formed integrally with the cylinder inner wall 71 on a plane defined by the Y axis and the Z axis so as to close one end of the cylinder 70, and a ring-shaped attachment seat 73 formed on another end of the cylinder inner wall 71. The cylinder inner wall 71 takes the same shape as the cylinder inner wall 82 of the first embodiment or a substantially kidney type shape corresponding to the shape of the lining 9.
The cylinder 70 and the adjustor attachment recess portions 12a, 12b are formed symmetrically about the center line Ozy of the brake caliper 10 shown in
The ring-shaped attachment seat 73 is formed on a plane defined by the Y axis and the Z axis on one end of the cylinder inner wall 71. A peripheral edge portion of the guide frame 65 is fixed to the attachment seat 71 by a plurality of bolts 66. Further, the peripheral edge portion 76 of the diaphragm 75 is sandwiched between the peripheral edge portion of the guide frame 65 and the attachment seat 73.
The diaphragm 75 is constituted by the peripheral edge portion 76, the bellows portion 77, which expands from the peripheral edge portion 76 toward the bottom portion 72 along the cylinder inner wall 71 and then curves back substantially 180 degrees inward, and the piston pressing portion 79, which forms a parallel plane to the brake pad 7 on the inside of the bellows portion 77. The peripheral edge portion 76, bellows portion 77, and piston pressing portion 79 are formed integrally from an elastic material such as rubber. The piston pressing portion 79 has a planar form which is slightly smaller than, but similar to, the transverse section of the cylinder 70 defined by the cylinder inner wall 71.
A back surface plate 62 is attached to a back surface of the piston pressing portion 79 of the diaphragm 75. The back surface plate 62 is fixed to the piston pressing portion 79 by a plurality of bolts 67. The back surface plate 62 is formed from a plate material having a substantially identical shape to the piston pressing portion 79. The bolts 67 are disposed at substantially equal intervals around the peripheral edge portion of the back surface plate 62.
By providing the diaphragm 75 with the above constitution, the cylinder inner wall 71 is positioned on the inside of the pressure chamber 63, in contrast to the cylinder inner wall 82 of the first embodiment.
Similar favorable effects to those of the first embodiment are obtained in this embodiment.
Moreover, in this embodiment, the back surface plate 62 is attached to the piston pressing portion 79, and therefore the rigidity of the piston pressing portion 79 can be improved. It should be noted that the back surface plate 62 may be attached to a front surface of the piston pressing portion 79. Alternatively, the back surface plate 62 may be omitted.
The contents of Tokugan 2007-288915, with a filing date of Nov. 6, 2007 in Japan, are hereby incorporated by reference.
Although the invention has been described above with reference to certain embodiments, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, within the scope of the claims.
The invention was described above using several specific embodiments, but this invention is not limited to the above embodiments, and a person skilled in the art may add various corrections or modifications to these embodiments within the technical scope of the claims.
For example, in the above embodiments, the frictional surfaces 6 formed on either side of the vehicle wheel 5 are sandwiched between the pair of brake pads 7. However, this invention may be applied to a caliper brake device in which the frictional surfaces 6 are formed on the respective surfaces of a rotor that rotates integrally with the vehicle wheel 5 such that these frictional surfaces 6 are sandwiched between the brake pads 7.
As described above, with the caliper brake device according to this invention, a pressing force for pressing a brake pad against a rotary body can be made even. Hence, when the caliper brake device according to this invention is applied to a vehicle wheel braking device for a railway vehicle, in which a great brake pad pressing force is required, a particularly favorable effect is obtained.
The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-288915 | Nov 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/070631 | 11/6/2008 | WO | 00 | 5/4/2009 |
