SELF-STEERING PLATFORM CAR

Abstract

 Problem to be Solved
A self steering truck having excellent turning performance is provided.
Solution
A main frame (1) having a rectangular frame shape in a plan view, and sub frames (2) provided at the front and rear of the main frame (1) based on the running direction form the base structure of the self steering truck. Axles (4) and (4) of right and left drive wheels (3) and (3) are rotatably supported on the main frame (1) via axle boxes (5) and (5). The sub frame (2) includes right and left swing arms (6) and (6) whose proximal end portions are pivotably supported on the main frame (1) in a horizontal plane, and a coupling link (7) for coupling the distal end portions of the swing arms (6) and (6). The length of the coupling link (7) is equal to the length between the proximal end portions of the swing arms (6) and (6). A parallelogram link is thereby formed between the sub frame (2) and the main frame (1).

Description

Technical Field

[0001] The present invention relates to a truck for supporting a railway vehicle, and more particularly, to a self steering truck having excellent sharp turning performance such as a truck for an LRT (light rail transit) vehicle.

Background Art

[0002] For railway vehicles, turning performance and running stability are required. The turning performance is achieved by a self steering function based on the tread gradient of a wheel. The self steering function can be improved by freeing the yawing of a wheel axle. However, when the yawing of a wheel axle is freed, a self-excited vibration called hunting oscillation occurs, to thereby deteriorate the running stability.
To improve the self steering function, a monocycle independently-rotatable truck in which independently-rotatable wheel units (axle and wheel) are provided on the right and left sides of a bogie frame is preferably employed. Examples of the related art regarding the monocycle independently-rotatable truck include Patent Document 1, Patent Document 2, and Non-Patent Document 1.

[0003] Patent Document 1 discloses a structure in which axle arms are coupled to the right and left sides of a truck frame having a square U shape respectively via two links, right and left wheels are rotatably supported on the right and left axle arms, and the right and left axle arms are coupled together via a link in the width direction. Also, Non-Patent Document 1 discloses a basic point regarding the monocycle independently-rotatable truck.

[0004] In Patent Document 2, it is proposed to solve a response delay of a wheel to a curve by arranging a steering assist actuator such as an electromagnetic damper based on the disclosures in Patent Document 1 and Non-Patent Document 1.

[0005] Also, Patent Document 3 proposes a single truck obtained by swingably coupling two truck frames together. In the truck, a front-side truck and a rear-side truck are coupled together through a pin, and a wheel unit where right and left wheels are mounted on a single axle is provided in each of the trucks.

[0006] 

Patent Document 1
Japanese Patent Laid-Open No. 2002-302038

Patent Document 2
WO 2006/075756

Patent Document 3
Japanese Patent Laid-Open No. 02-293253

Non-Patent Document 1

[0007] Fritz Frederich, Possibilities as yet unknown or unused regarding the wheel/rail tracking mechanism, Development of modem rolling stock running gear, Rail International, November 1985, p33

Disclosure of the Invention

Problems to be Solved by the Invention

[0008] None of Patent Documents 1 and 2 and Non-Patent Document 1 disclosing the truck clearly describes the relationship between a drive wheel and a steering wheel. Particularly, to allow a vehicle to smoothly run on a track with a very small radius of curvature such as a light rail transit vehicle, it is considered preferable that the drive wheel and the steering wheel be as close as possible to each other. However, there is no disclosure on the point.

[0009] Since the truck disclosed in Patent Document 3 is based on the single axle truck where the right and left wheels are mounted on the single axle, the truck has limited turning performance, and is thus not suitable for the track of LRT or the like with a very small radius of curvature such as a light rail transit vehicle.

Means for Solving the Problems

[0010] To solve the aforementioned problems, in a self steering truck according to the present invention, a single truck includes a main frame and a sub frame, wherein right and left drive wheels are rotatably supported on the main frame, the sub frame includes right and left swing arms whose proximal end portions are supported on the main frame in a swingable manner in a yawing direction and a link for coupling the arms, and independently-rotatable steering wheels having a self steering function are provided on the right and left swing arms.

[0011] Although the sub frame may be provided at only one of the front and rear of the main frame, it is preferable to provide the sub frame at each of the front and rear of the main frame in view of stability. When the sub frames are provided at both the front and rear of the main frame, the front and rear sub frames are coupled together via a link mechanism such that the steering wheels mounted on the front and rear sub frames are in opposite phase. Accordingly, the stability is improved and a higher response to a small radius of curvature is obtained.

[0012] A basic shape of a link formed by one side of the main frame and the sub frame is a parallelogram where the length of the coupling link that constitutes the sub frame is equal to the length between the proximal end portions of the right and left swing arms. However, when the length of the coupling link is made larger than the length between the proximal end portions of the right and left swing arms, the radius of rotation of an inner wheel can be made smaller than the radius of rotation of an outer wheel during yawing. That is, an Ackerman steering mechanism can be formed. The Ackerman steering mechanism is a preferable structure for a curve with a very small radius of curvature.

[0013] A damper for damping the swing of the sub frame, or an electromagnetic damper also having a function of actively controlling the swing of the sub frame may be provided between the main frame and the sub frame.

Advantages of the Invention

[0014] According to the present invention, the drive wheels and the steering wheels are provided in the single truck, and the steering wheels are mounted on the sub frame that is swingable relative to the main frame on which the drive wheels are mounted. Accordingly, the self steering truck having excellent turning performance can be obtained.
Particularly, by employing a monocycle independent type wheel for all the wheels including the drive wheels, no axle is extended over the width direction of a vehicle. Thus, the self steering truck is also preferable for a low floor type vehicle.

Brief Description of the Drawings

[0015] 

Figure 1 is a plan view of a self steering truck according to the present invention;

Figure 2 is a plan view for explaining the motion of the self steering truck shown in Figure 1 at the time of turning a curve;

Figure 3 is a plan view of a self steering truck according to another embodiment;

Figure 4 is a plan view for explaining the motion of the self steering truck shown in Figure 3 at the time of turning a curve;

Figures 5(a) and 5(b) are plan views of a self steering truck according to another embodiment;

Figure 6 is a plan view of a self steering truck according to another embodiment;

Figures 7(a) and 7(b) are plan views of a self steering truck according to another embodiment;

Figure 8 is a plan view of a self steering truck according to another embodiment;

Figure 9 is a plan view of a self steering truck according to another embodiment;

Figures 10(a) and 10(b) are plan views of a self steering truck according to another embodiment;

Figures 10(c) and 10(d) are plan views of a self steering truck according to another embodiment;

Figures 11(a) to 11(c) are enlarged side views illustrating an application example to a railway vehicle; and

Figures 12(a) to 12(d) are side views illustrating an application example to a railway vehicle.

Description of Symbols

[0016] 

1:

Main frame

2:

Sub frame

3:

Drive wheel

4:

Axle

5:

Axle box

6:

Swing arm

7:

Coupling link

8:

Steering wheel

9:

Axle

10:

Axle box

11:

Direct acting damper

12:

Rotating damper

13, 14:

Link mechanism

15:

Bolsterless air spring

16:

Mono link

17:

Wing spring

18:

Guide member

L1:

Distance between a drive wheel and the proximal end portion of a swing arm

L2:

Distance between a steering wheel and the proximal end portion of a swing arm

R1:

Outer rail

R2:

Inner rail

Best Mode for Carrying Out the Invention

[0017] In the following, a best mode for carrying out the present invention will be described in detail with reference to the drawings. Figure 1 is a plan view of a self steering truck according to the present invention. Figure 2 is a plan view for explaining the motion of the self steering truck shown in Figure 1 at the time of turning a curve.

[0018] A main frame 1 having a rectangular frame shape in a plan view and sub frames 2 provided at the front and rear of the main frame 1 based on the running direction form the base structure of the self steering truck according to the present invention.

[0019] Axles 4 and 4 of right and left drive wheels 3 and 3 are rotatably supported on the main frame 1 via axle boxes 5 and 5. The same drive torque is applied to the right and left drive wheels 3 and 3 by use of a series motor or a differential gear.
In a case of using the independent wheels as shown in the drawings or in a case of using wheels with no flange described below, a cylindrical tread is employed as the tread shape of the drive wheels 3 and 3. In a case of using integrated wheels with an axle, a conical or circular tread is preferably employed.

[0020] The sub frame 2 includes right and left swing arms 6 and 6 whose proximal end portions are pivotably supported on the main frame 1 in a horizontal plane, and a coupling link 7 for coupling the distal end portions of the swing arms 6 and 6 together to constitute a link. The length of the coupling link 7 is set to be equal to the length between the proximal end portions of the swing arms 6 and 6. A parallelogram link is thereby formed between the sub frame 2 and the main frame 1.

[0021] An axle 9 of a steering wheel 8 is rotatably supported on each of the swing arms 6 and 6 via an axle box 10. A distance L1 between the drive wheel 3 (the center of the axle 4) and the proximal end portion (a joint portion) of the swing arm 6 is set to be equal to a distance L2 between the steering wheel 8 (the center of the axle 9) and the proximal end portion of the swing arm 6.

[0022] With the aforementioned configuration, when a vehicle passes through a curved rail track, the swing arm 6 swings along the curve of the rail track, and a steering angle is generated in the steering wheel 8 as shown in Figure 2. Accordingly, the vehicle can smoothly yaw with substantially no angle of attack.

[0023] Also, since the distance L1 is equal to the distance L2 in the parallelogram link, the drive wheel 3 travels on the same arc as the steering wheel 7. The setting is suitable for a relatively gentle curve where the radius of curvature of an outer rail R1 and the radius of curvature of an inner rail R2 can be considered equivalent to each other.

[0024] Figure 3 is a plan view of a self steering truck according to another embodiment. Figure 4 is a plan view for explaining the motion of the self steering truck shown in Figure 3 at the time of turning a curve. In the embodiment, the length of the coupling link 7 is set to be larger than the length between the proximal end portions of the swing arms 6 and 6, to thereby form a trapezoidal link, that is, an Ackerman steering mechanism between the sub frame 2 and the main frame 1.

[0025] The Ackerman steering mechanism is a mechanism in which an inner wheel has a smaller radius of rotation than that of an outer wheel during yawing as shown in Figure 4. The structure is thus preferable in a case where the curve has a very small radius of curvature since there is a large difference between the radii of curvature of the outer rail R1 and the inner rail R2.

[0026] Figures 5(a) and 5(b) are plan views of a self steering truck according to another embodiment. In the embodiment, while an Ackerman steering link is employed as the structure of the sub frames 2 coupled to the front and rear of the main frame 1, the drive wheels are not provided in the main frame 1.

[0027] Figure 6 is a plan view of a self steering truck according to another embodiment. In the embodiment, a damper for damping the swing of the sub frame 2 is provided between the main frame 1 and the sub frame 2. As the damper, a direct acting electromagnetic damper 11 or a rotating electromagnetic damper 12 may be employed as well as a normal damper that exerts a hydraulic or air damping force. When the electromagnetic damper is applied as described above, the swing of the sub frame 2 is not only damped to stabilize the operation, but the swing of the sub frame can be also actively controlled in association with the curve of a track.

[0028] Figures 7(a) and 7(b) are plan views of a self-steering truck according to another embodiment. In the embodiment shown in Figure 7(a), the front end of the left-side swing arm 6 of the front sub frame 2 is coupled to the rear end of the right-side swing arm 6 of the rear sub frame 2 via a link mechanism 13 such that the steering wheel 8 of the front sub frame 2 is in opposite phase to the steering wheel 8 of the rear sub frame 2. Similarly, in Figure 7(b), the left-side swing arm 6 of the front sub frame 2 is formed into an L shape, and the right-side swing arm 6 of the rear sub frame 2 is formed into an L shape. A link mechanism 14 couples the L-shaped arms together such that the steering wheels are in opposite phase. By allowing the front and rear steering wheels to be in opposite phase as described above, the vehicle can smoothly run along a curve with a very small radius of curvature.

[0029] Figure 8 is a plan view of a self steering truck according to another embodiment. In the embodiment, the sub frame 2 is provided at only one of the front or rear ends of the main frame 1. The configuration is effective in a case where the vehicle is short and only one sub frame can be coupled thereto or in a case of a one-way operation.

[0030] Figure 9 is a plan view of a self steering truck according to another embodiment. In the embodiment, a single axle 4 is mounted on the main frame 1, and the drive wheels 3 and 3 are mounted on the both ends of the axle 4. Although the structure is disadvantageous to a low floor type, a mechanism for transmitting a drive force can be simplified.

[0031] Figures 10(a) to 10(d) are plan views of a self-steering truck according to another embodiment. In the embodiment shown in Figure 10(a), a flange for preventing derailment is not provided in the drive wheel 3. This is because the front and rear steering wheels have flanges and the drive wheel is thus not required to have a flange.
In the embodiment shown in Figures 10(b) to 10(d), the drive wheel 3 is made of rubber, or a rubber layer is formed on the surface of the drive wheel 3. In a type shown in Figure 10(b), the rubber drive wheel 3 is placed on a rail, so that the vehicle runs by a frictional force with the rail. Even when the drive wheel 3 is in contact with the rail as described above, a load applied to the rail can be considerably reduced and the drive force can be increased by employing the rubber drive wheel 3.
In a type shown in Figure 10(c), the single rubber drive wheel 3 is arranged in the intermediate portion of the main frame 1 in the width direction. In the type, the vehicle runs by friction not with the rail but with a track surface. Thus, it is necessary to make the surface between the outer rail and the inner rail flat with asphalt or concrete. In the type, the rail works only for a steering operation and is thus subject to less wear. Therefore, the rail requires less maintenance.
In a type shown in Figure 10(d), the rubber drive wheel 3 is arranged outside the main frame 1. In the truck according to the type, a smaller load is applied to the rail as in the aforementioned type. Also, since the drive wheels 3 project to the right and left, the running stability is improved regardless of running on a straight track or a curved track. The configuration is effective especially when the vehicle has a narrow gauge.

[0032] Figures 11(a) to 11(c) are enlarged side views illustrating an application example to a railway vehicle. In types shown in Figures 11(a) and 11(b), a bolsterless air spring 15 is arranged between the vehicle and the self steering truck, and a mono link 16, a wing spring 17, or a guide member 18 are used as a method for supporting the axle box. The drive wheel may have a larger diameter, and the steering wheels may have smaller diameters while the diameters of the front and rear steering wheels are different from each other as shown in Figure 11(c).
The load share ratio of the drive wheel is made largest as shown in the drawings, so that the drive force of the drive wheel can be increased.

[0033] Figures 12(a) to 12(d) are side views illustrating an application example to a railway vehicle. In a type shown in Figure 12(a), the self steering truck according to the present invention is applied to the front and rear of a single vehicle. In a type shown in Figure 12(b), the self steering truck according to the present invention is applied to a coupling portion between two vehicles. In a type shown in Figure 12(c), the self steering truck according to the present invention is applied to each of three coupled vehicles. In a type shown in Figure 12(d), the self steering truck according to the present invention is applied to vehicles on the both ends of three coupled vehicles excluding an intermediate vehicle.

Claims

1. A self steering truck for supporting a railway vehicle, the truck comprising a main frame and a sub frame, wherein right and left drive wheels are rotatably supported on the main frame, the sub frame comprises right and left swing arms whose proximal end portions are supported on the main frame in a swingable manner in a yawing direction and a link for coupling the arms, and independently-rotatable steering wheels having a self steering function are provided on the right and left swing arms.

2. A self steering truck for supporting a railway vehicle, the truck comprising a main frame and a sub frame, wherein a rubber drive wheel is rotatably supported on the main frame, the sub frame comprises right and left swing arms whose proximal end portions are supported on the main frame in a swingable manner in a yawing direction and a link for coupling the arms, and independently-rotatable steering wheels having a self steering function are provided on the right and left swing arms.

3. The self steering truck according to claim 1 or 2, wherein the sub frame is provided at each of a front and a rear of the main frame.

4. The self steering truck according to claim 3, wherein the front and rear sub frames are coupled together via a link mechanism such that the steering wheels mounted on the front and rear sub frames are in opposite phase.

5. The self steering truck according to claim 1 or 2, wherein a length of the coupling link that constitutes the sub frame is equal to a length between the proximal end portions of the right and left swing arms to thereby form a parallelogram link.

6. The self steering truck according to claim 1 or 2, wherein a distance (L1) between a center of an axle of the drive wheel and the proximal end portion of the swing arm is set to be equal to a distance (L2) between a center of an axle of the steering wheel and the proximal end portion of the swing arm.

7. The self steering truck according to claim 1 or 2, wherein a length of the coupling link that constitutes the sub frame is larger than a length between the proximal end portions of the right and left swing arms to thereby form an Ackerman steering mechanism.

8. The self steering truck according to any one of claims 1 to 7, wherein a damper for damping swing of the sub frame, or an electromagnetic damper also having a function of actively controlling the swing of the sub frame is provided between the main frame and the sub frame.

Drawing