DAMPING DEVICE

Abstract

A damping device, including: a wedge assembly having a wedge including a vertical surface and an inclined surface; a primary friction board disposed on the vertical surface; and a secondary friction board disposed on the inclined surface; and a damping spring assembly disposed underneath the wedge assembly. The wedge assembly has the following structure parameters: α=16-30°, and μ

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a damping device, and more particularly to a damping device for a wedge of a wheel truck of a railroad freight car.

2. Description of the Related Art

As a critical part of a freight car, a typical wheel truck of a railroad freight car includes two side frame assemblies and a bolster assembly. Journal-box guides disposed on two ends of the side frame assembly are fixed on a front wheel pair and a rear wheel pair via roller bearing adapters and bearing assemblies, respectively. The bolster assembly has two ends, each of which is mounted in a central square hole of the side frame assembly via a spring suspension device. The spring suspension device is used to support the load of the bolster assembly and includes a bearing spring unit in the center and two frictional damping devices for a wedge on both sides.

The existing frictional damping device includes a wedge assembly and a damping spring assembly underneath the wedge assembly. A vertical primary friction surface and an inclined secondary friction surface of the wedge assembly are attached to a column surface of the side frame assembly and an inclined surface of the bolster assembly, respectively.

The wheel truck of a railroad freight car, as described above, is advantageous in its simple structure, uniform distribution of the load, low cost in production and maintenance. However, the connection between the bolster assembly and the side frame assembly is loose and the diamond resistant rigidity is low, which cannot resist the violent shaking between the bolster assembly and the side frame assembly. And when the wheel truck runs on a curved rail track, the attack angle between the wheel pairs and the rail enlarges, thereby resulting in damages on the wheel and the rail. Particularly, the wedge of the spring suspension device has a relative larger apex angle, that is, the angel between the secondary friction surface and a vertical plane is about 35-70°. Thus, the diamond resistant rigidity is highly limited. When the bolster assembly moves downwards relative to the side frame assembly, a vertical force component of a force from the inclined surface to the wedge is larger than a sum of vertical force components of the friction produced on the primary friction surface of the wedge and the friction produce on the secondary friction surface of the wedge, so that the wedge moves downwards, and the vertical distance between the bolster assembly and the side frame assembly becomes smaller, thereby resulting in relative rotation between the bolster assembly and the side frame assembly, as well as diamond deformation. In such a condition, the critical speed of the wheel truck is low, which limits the running speed and running performance of the freight car, and cannot meet the requirement of the speed-raising freight car.

To solve the above problems, the current speed-raising trains employs a cross supporting device between two side frame assembly or a spring plank for improving the diamond resistant rigidity of the conventional wheel truck. The problem is that, such a cross supporting device or spring plank has a complicated structure, heavy weight, and high production and maintenance costs. Thus, it is very significant to improve the diamond resistant rigidity of the conventional wheel truck and the dynamic performance of the trains.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of the invention to provide a damping device that has a simple structure, low production and maintenance costs, superb dynamic performance for crossing curved tracks, and can meet high requirements of the diamond resistant rigidity for speed-raising trains.

To achieve the above objective, in accordance with one embodiment of the invention, there is provided a damping device comprising a wedge assembly and a damping spring assembly disposed underneath the wedge assembly. The wedge assembly comprises a wedge, a primary friction board disposed on a vertical surface of the wedge, and a secondary friction board disposed on an inclined surface of the wedge. The wedge assembly is provided with the following structure parameters: α=16-30°, and μ<tgα<μ+μ₁. Of them, α represents an included angle between a friction surface of the secondary friction board and a vertical plane; μ represents a friction coefficient of the primary friction board; and μ₁ represents a friction coefficient of the secondary friction board.

The included angle α of the wedge assembly is no more than 30°, which is much smaller than the conventional vertex angle of 35-70°, and meets the requirement that tgα<μ+μ₁. Thus, when the bolster assembly moves in a horizontal direction relative to the side frame assembly, a downward vertical force component of a force exerted on the wedge assembly from the inclined surface of the bolster remains smaller than a sum of upward vertical force components of the friction produced on the primary friction board and the friction produced on the secondary friction board, so that the wedge assembly is prevented from moving downwards, relative rotation between the bolster assembly and the side frame assembly cannot occur, and a high diamond resistant rigidity is maintained between the bolster assembly and the side frame assembly. Supposing that, the angle α is too small and approximates to the friction angle of the primary friction board of the wedge assembly, the wedge assembly will be self-limited once the bolster assembly moves downwards relative to the side frame assembly, thereby lowering the dynamic performance of the wheel truck. Therefore, the lower bound of the angle α of the wedge assembly is designed as 16°, and μ<tgα, to make sure that the wedge assembly moves freely during the vertical movement of the bolster assembly, and the wheel truck has a good dynamic performance for crossing curved tracks.

In a class of this embodiment, a width of the wedge assembly is L=200-600 mm, which is at least 1.3 times longer than the width of the conventional wedge having a variable friction. The wedge having a variable friction herein means that a wedge is disposed on a damping spring which is arranged in a square hole in a center of a side frame, the damping friction exerted on the wedge changes in proportional to the variable vertical load exerted on the bolster assembly. Not only does the width design of the wedge assembly increase the length of the torque arm to resist the diamond deformation between the bolster assembly and the side frame assembly; but also it increases attached area between the primary friction board and the column surface of the side frame assembly, and between the secondary friction board and the inclined surface of the bolster assembly, so that the diamond resistant rigidity between the bolster assembly and the side frame assembly is further improved.

In a class of this embodiment, a mechanical property of the damping spring meets the following relation formula: K₁×ctgα=K×C/2μ, in which, K₁ represents a rigidity of the damping spring assembly; K represents a total rigidity of a spring suspension device; C represents a relative friction coefficient of the wheel truck and ranges from 0.05 to 0.15; and μ represents a friction coefficient of the primary friction board. As the rigidity K₁ of the damping spring assembly is inversely proportional to ctgα of the wedge assembly, K₁ can be adjusted according to the value of angle α, thereby maintaining a suitable friction damping force, and preventing frictions from being too large during movements in vertical and horizontal directions.

In a class of this embodiment, the secondary friction board is in connection with the inclined surface of the wedge via a spherical structure comprising a convex surface and a corresponding concave surface, which ensures good contact between the secondary friction board and the inclined surface of the bolster, as well as good contact between the primary friction board and the column surface. Thus, the reliability of the diamond resistance of the bolster assembly and the side frame assembly is highly improved, and at the same time, damages on the inclined surface of the bolster and the maintenance cost are largely decreased.

Advantages of the invention are summarized hereinbelow:

First of all, the wedge assembly of the damping device not only assures a free movement of the wedge assembly when the bolster moves in a vertical direction, but also prevents the wedge assembly from moving when the bolster moves in a horizontal direction. Thus, the wheel truck has an enough high diamond resistant rigidity and good dynamic performance even without a crossed supporting device or a spring plank. Furthermore, the design of the width of the wedge assembly which is 1.3 times longer than that of the conventional also improves the diamond resistant rigidity and the dynamic performance, thereby highly improving the critical speed of the freight car, the capacity of crossing curved tracks, and the running performance. Finally, the wheel truck has a simple structure, light weight, and low production and maintenance costs, which is applicable to the new railroad freight car having a running speed of 120 km/h, and meets the requirements of the diamond resistant rigidity for the speed-raising trains.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to the accompanying drawings, in which:

FIG. 1 is a stereogram of a damping device in accordance with one embodiment of the invention;

FIG. 2 is a cross-sectional view of a damping device of FIG. 1;

FIG. 3 is a diagram of a damping device fitted with a bolster assembly and a side frame assembly in accordance with one embodiment of the invention;

FIG. 4 is a force balance diagram of a damping device as shown in FIG. 3 during a movement of a bolster in horizontal direction; and

FIG. 5 is a force balance diagram of a damping device as shown in FIG. 3 during a movement of a bolster downwards in vertical direction.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To further illustrate the invention, experiments detailing a damping device are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

As shown in FIGS. 1 and 2, a damping device for a wedge of a wheel truck of a railroad freight car comprises a wedge assembly 1 and a damping spring assembly 2 disposed underneath the wedge assembly 1. The wedge assembly 1 comprises a wedge 1b comprising a vertical surface and an inclined surface, a primary friction board 1a is disposed on the vertical surface, and a secondary friction board 1c is disposed on the inclined surface. Structure parameters of the wedge assembly 1 are as follows: L=200-260 mm, α=16-30°, and μ<tgα<μ+μ₁. Of them, L represents a width of the wedge assembly 1; α represents an included angle between a friction surface of the secondary friction board 1c and a vertical plane; μ represents a friction coefficient of the primary friction board 1a; and μ₁ represents a friction coefficient of the secondary friction board 1c. According to the designing requirement of the value of the angle α, suitable materials of the primary friction board 1a and the secondary friction board 1b can be selected and structures thereof can be properly adjusted to make the values of μ and μ₁ meet their requirements.

As a supporting base, the wedge 1b is made of steel or iron to meet the required intensity and rigidity. Two secondary friction boards 1c, being made of modified nylon materials, are symmetrically disposed on the inclined surface of the wedge 1b. The connection between the secondary friction board 1c and the inclined surface of the wedge 1b is achieved by a spherical structure comprising a convex surface and a corresponding concave surface. As shown in FIG. 2, a convex spherical surface of the secondary friction board 1c is received by a corresponding concave spherical surface of the inclined surface of the wedge 1b. The structural design of the secondary friction board 1c is advantageous in that: on one hand, the convex spherical surface of the secondary friction board 1c matches well with the concave spherical surface of the inclined surface of the wedge 1b, which assures the well contact between the secondary friction board 1c and the inclined surface of the bolster, even when deviations occur in the apex angle α of the wedge assembly 1, the angel and the flatness of the inclined surface of the bolster. Thus, the wedge assembly 1 and the secondary friction board 1c can maintain stable, and a large friction is produced to prevent the wedge assembly 1 from moving downwards when diamond deformations occurs between the bolster unit and the side frame assembly, thereby effectively improve the diamond resistant rigidity of the wheel truck; on the other hand, the secondary friction board 1c made of modified nylon materials has a good abrasive resistance and high friction coefficient, not only is the secondary friction board 1c hard-wearing, but also it alleviates the abrasion on the inclined surface of the bolster, thereby being convenient to fix and replace, and lowering the production cost. The primary fiction board 1a is an integrated friction board made of polymer materials that can be fixed in a slot on the vertical surface of the wedge 1b via fasteners. Also, the convex spherical surface of the secondary friction board 1c and the matched concave spherical surface of the inclined surface of the wedge 1b assure the well contact between the primary friction board 1a and column surface of the side frame when deviation occurs in the apex angle α of the wedge assembly 1, the flatness of the inclined surface of the bolster, and the column surface of the side frame. Thus, a stable damping property of the wedge assembly 1 is achieved.

As shown in FIG. 3, as a part of a spring suspension device, the damping device is disposed between the side frame assembly 3 and the bolster assembly 4. A lower part of the damping spring assembly 2 is disposed on a spring plank in the square hole of the side frame assembly 3. The primary friction board 1a of the wedge assembly 1 is attached to the column surface 3a of the side frame; and the two secondary friction boards 1c of the wedge assembly 1 are attached to the inclined surface 4a of the bolster. Thus, the function of frictional damping is achieved in the running of the freight car.

As shown in FIG. 4, when the bolster assembly 4 moves in a horizontal direction relative to the side frame assembly 3, the inclined surface 4a of the bolster assembly exerts a force N on the wedge assembly 1, then, a fiction F_f is produced between the inclined surface 4a of the bolster assembly and the secondary friction board 1c of the wedge assembly 1, and a fiction F_z is produced between the column surface 3a of the side frame assembly and the primary friction board 1a of the wedge assembly 1. It is known from FIG. 4 that a vertical force component of N is N_y=N×sin α, and a horizontal force component of N is N_z=N×cos α. In addition, two upward frictions are exerted on the wedge assembly 1 on the primary friction board 1a and the secondary friction board 1c, respectively, in which, the friction produced on the primary friction board 1a is F_z=N_z×μ=N×cos α×μ, and the friction produced on the secondary friction board 1c is F_f=N×μ₁. According to the requirement that N_y<F_z+F_f×cos α, that is, N×sin α<N×cos α×μ+N×μ₁×cos α, a relation formula tgα<μ+μ₁ is acquired after simplification. Thus, the wedge assembly 1 is limited by the frictions produced on the primary friction board la and the secondary friction board 1c from moving downwards, and an enough high diamond resistant rigidity between the bolster assembly 4 and the side frame assembly 3 is achieved.

As shown in FIG. 5, when the bolster assembly 4 moves downwards in a vertical direction relative to the side frame assembly 3, the inclined surface 4a of the bolster assembly exerts a force N on the wedge assembly 1, then, a fiction F_f is produced between the inclined surface 4a of the bolster assembly and the secondary friction board 1c of the wedge assembly 1, and a fiction F_z is produced between the column surface 3a and the primary friction board 1a of the wedge assembly 1. It is known from FIG. 5 that a vertical force component of N is N_y=N×sin α, and a horizontal force component of N is N_z=N×cos α. At this moment, two frictions are exerted on the wedge assembly 1, of them, the friction produced on the primary friction board 1a F_z is upward, and the friction produced on the secondary friction board 1c F_f is downward, and F_z=N_z×μ=N×cos α×μ. According to the requirement that F_z<N_y, that is, N×cos α×μ<N×sin α, a relation formula μ<tgα is acquired after simplification. In such a way, the wedge assembly 1 isn't limited by the friction produced on the primary friction board 1a, and can move freely when the bolster assembly 4 moves in vertical direction, thereby achieving a normal attenuation vibration of the wheel truck during the running of the freight car.

It is also known from FIG. 5 that the damping force exerted on the wedge assembly 1 is mainly from the friction F_z produced on the primary friction board 1a, and F_z is relevant to a bearing capacity P of the damping spring assembly 2. The relation formula between F_z and P is F_z=P×ctgα×μ, in which, P=K₁×y. K₁ represents a rigidity of the damping spring assembly 2; and y represents a flexibility of the damping spring assembly 2. Thus, the formula above is converted as F_z=K₁×y×ctgα×μ. In order to remain a suitable damping force for the wedge assembly 1, a mechanical property of the damping spring assembly 2 should meet the following requirement: K₁×ctgα=K×C/2μ, in which, K represents a total rigidity of the spring suspension device, and C represents a relative friction coefficient of the wheel truck and ranges from 0.05 to 0.15. As values of K and μ are determined by the designing requirements, when angle α is decreased, ctgα decreases correspondingly, and the damping spring assembly 2 should be selected from materials having a lower rigidity K₁, to make the relative friction coefficient of the wheel truck remains in the range of 0.05-0.15, and to prevent frictions from being too large during movements in vertical and horizontal direction.

The above damping device of the wheel truck of the freight car, has a high diamond resistant rigidity, high critical speed, and superb dynamic performance for crossing curved tracks, even without adopting a crossed supporting device or a spring plank. Thus, it is applicable to the new railroad freight car having a running speed of 120 km/h, and meets the requirement for speed-raising.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims

1. A damping device, comprising: a) a wedge assembly (1) comprising a wedge (1b) comprising a vertical surface and an inclined surface; a primary friction board (1a) disposed on the vertical surface; and a secondary friction board (1c) disposed on the inclined surface; andb) a damping spring assembly (2) disposed underneath the wedge assembly (1);

2. The damping device of claim 1, wherein a width of the wedge assembly (1) is L=200-260 mm

3. The damping device of claim 1, wherein a mechanical property of the damping spring assembly (2) meets the following formula: K1×ctgα=K×C/2μ, in which K1 represents a rigidity of the damping spring assembly (2), K represents a total rigidity of a spring suspension device, and C represents a relative friction coefficient of the wheel truck of a railroad freight car and ranges from 0.05 to 0.15.

4. The damping device of claim 2, wherein a mechanical property of the damping spring assembly (2) meets the following formula: K1×ctgα=K×C/2μ, in which K1 represents a rigidity of the damping spring assembly (2), K represents a total rigidity of a spring suspension device, and C represents a relative friction coefficient of the wheel truck of a railroad freight car and ranges from 0.05 to 0.15.

5. The damping device of claim 1, wherein the secondary friction board (1c) is in connection with the inclined surface of the wedge (1b) via a spherical structure comprising a convex surface and a corresponding concave surface.

6. The damping device of claim 2, wherein the secondary friction board (1c) is in connection with the inclined surface of the wedge (1b) via a spherical structure comprising a convex surface and a corresponding concave surface.

7. The damping device of claim 3, wherein the secondary friction board (1c) is in connection with the inclined surface of the wedge (1b) via a spherical structure comprising a convex surface and a corresponding concave surface.

8. The damping device of claim 4, wherein the secondary friction board (1c) is in connection with the inclined surface of the wedge (1b) via a spherical structure comprising a convex surface and a corresponding concave surface.

9. The damping device of claim 5, wherein two secondary friction boards (1c) are symmetrically disposed on the inclined surface of the wedge (1b).

10. The damping device of claim 6, wherein two secondary friction boards (1c) are symmetrically disposed on the inclined surface of the wedge (1b).

11. The damping device of claim 7, wherein two secondary friction boards (1c) are symmetrically disposed on the inclined surface of the wedge (1b).

12. The damping device of claim 8, wherein two secondary friction boards (1c) are symmetrically disposed on the inclined surface of the wedge (1b).

13. The damping device of claim 1, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.

14. The damping device of claim 2, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.

15. The damping device of claim 3, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.

16. The damping device of claim 4, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.

17. The damping device of claim 5, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.

18. The damping device of claim 6, wherein the wedge (1b) is made of steel or iron;the primary friction board (1a) is made of polymer materials; andthe secondary friction board (1c) is made of modified nylon materials.