Articulation damping device for articulated buses.

The invention relates to a joint damping device for use in an articulated bus with a front end and a follower connected to it via a swivel head (swivel joint), at least two hydraulic cylinders or shock absorbers being arranged between the two end components.

Such a joint damping device is known according to P ...... (patent application P 39 12 383.9-21). By means of this device, a characteristic of the damping torque is achieved, according to which a damping torque is built up even with the slightest deviation from driving straight ahead, which increases approximately sinusoidally with increasing bending angle.

The invention has for its object to provide a joint damping device of the known characteristics with simpler means and thus less expensive.

This is achieved according to the invention in that the hydraulic cylinder or shock absorber attached between the front carriage and the follower connected to the outer ring of the slewing ring or between the follower and the front carriage connected to the inner ring slewing ring with one end articulated on the front carriage or follower on both sides of the longitudinal median plane and at a distance from one another and with its other end articulated on the respective turntable part on or near the longitudinal median plane, are arranged at an acute angle to it and the inner dead position of the hydraulic cylinder or shock absorber pivoting outwards is only reached after a certain deflection of the joint from the longitudinal center plane. It is possible in this way that the two hydraulic cylinders or shock absorbers have the same length, the same stroke and the same diameter, as a result of which both production and warehousing become more efficient. Both shock absorbers or hydraulic cylinders already have a lifting speed and a lever arm towards the center of the swivel joint when driving straight ahead with slight bending movements, which creates a corresponding damping torque. The increase in the damping torque above the articulation angle is approximately sinusoidal. In the arrangement according to the invention, the two hydraulic cylinders or shock absorbers can be mounted in a horizontal plane, which enables a low joint height and thus allows good passage for the cables and lines leading from one car part to the other. Larger damping moments can be achieved by increasing the spacing of the cylinder or shock absorber linkage points on the front end or trailer, although the stroke must also be increased accordingly. This possibility of varying the damping torque curve can possibly be very useful for the special operating conditions or to achieve optimal values.

According to a feature of the invention, an adjustable throttle valve is arranged in the connecting line between the connections of the displacement spaces of the hydraulic cylinder. In this way, the damping torque can be modified and, if necessary, adapted to the geographical or seasonal route conditions. An adjustable throttle valve can also be assigned to each connection in the connecting line between the connections of the hydraulic cylinder, the other connection being blocked via check valves.

According to another feature of the invention, it is provided that a plurality of throttle valves of different throttle cross-section connected in parallel are arranged in a line, the different throttle valves being switchable to different articulation angle ranges. In this way, particularly dangerous bending angle ranges can be clearly delimited.

By using a shut-off valve in the hydraulic circuit, constant damping results, which can be set as high as desired and which results from the assignment of a pressure relief valve. This higher constant damping can prove to be necessary, for example when driving out of parking bays or in suddenly occurring dangerous road conditions, for example on icy roads. Constant damping can be switched on based on the driver's subjective feeling at the push of a button or objectively controlled by an ABS / ASR system.

According to its alternative solution for the use of hydraulic cylinders, shock absorbers with different damping characteristics over the stroke can also be used.

The invention is shown and described in an exemplary embodiment.

Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>a joint damping device according to the invention in side view,</dd><dt>Fig. 2</dt><dd>a joint damping device according to the invention in plan view,</dd><dt>Fig. 3</dt><dd>a schematic representation of an articulated bus,</dd><dt>Fig. 4</dt><dd>a hydraulic circuit diagram,</dd><dt>Fig. 5</dt><dd>a diagram of cylinder stroke versus articulation angle,</dd><dt>Fig. 6</dt><dd>a diagram of the lifting speed over the bending angle,</dd><dt>Fig. 7</dt><dd>a diagram damping moment versus buckling angle.</dd></dl>

3 shows an articulated bus with a front end 3 and a rear end 6, which are connected to one another in an articulated manner via a slewing ring connection 1. The arrangement of the joint damping device according to the invention can be seen from FIGS. 1 and 2. A hydraulic cylinder 2 or shock absorber 2 ′ in FIG. 5 is articulated on the front end at a distance y from the longitudinal center plane. For this purpose, on the other side, likewise at a distance y from the longitudinal center plane, a hydraulic cylinder 19 or shock absorber 19 'is articulated in 5'. At the other end, the two cylinders 2, 19 or shock absorbers 2 ', 19' are connected in an articulated manner 4 in a vertical plane on the longitudinal center plane on the outer part of the slewing ring 1 '. In this position of the cylinders or shock absorbers, the articulated cable is traveling straight ahead. With x the distance between the articulation points 5, 5 'to articulation point 4 in the longitudinal center plane is designated, with b_min the inner dead position of the hydraulic cylinder or shock absorber, with a is the radius of the slewing ring, with angle β the articulation angle between front carriage 3 and trailer 6 Longitudinal median angle formed. If the follower 6 bends to the left, the hydraulic cylinder 2 or shock absorber 2 'and hydraulic cylinder 19 or Shock absorber 19 'to the right, the stroke decreasing from 2, 2' to point A and the stroke from 19, 19 'increasing to point A to the same extent. At point A, the moment of 2, 2 'is equal to 0. On the way beyond A, the moments of cylinders 2, 19 or shock absorbers 2', 19 'then add up.

5 is based on the following equation:<maths id="math0001" num=""><img file="EP0446614A2_D0001.tif" /></maths> The following equation is assigned to the lifting speed diagram according to FIG. 6.<maths id="math0002" num=""><img file="EP0446614A2_D0002.tif" /></maths>

According to the formula<maths id="math0003" num=""><img file="EP0446614A2_D0003.tif" /></maths> The torque curves M1 and M2 result, and the torque curve Mges in FIG. 7 results from this. The torque curve shows a practice-oriented, optimal curve of the damping torque characteristic curve, a moment being built up shortly after the 0 position, which counteracts a "wobbling" of the vehicle and with a larger buckling angle, the damping torque increases progressively to match the buckling risk.

FIG. 4 shows a hydraulic circuit diagram with a cylinder 2, 19, which has connections 10 and 11 at its ends, which are connected by a line 9. Throttle valves 12 and 13, which are adjustable on parallel connecting strands, are arranged along the further course of line 9. In each case one line can be acted on, since shut-off valves 14, 15 connected to one another are installed between the lines, between which a line runs, in which a pressure relief valve 16 is installed. To compensate for leakage losses and different stroke volumes, a pressure accumulator 18 is installed in the system. If throttle valves 12, 13 are arranged, these can be used to modify the damping torque. With the help of the shut-off valve 17, a constant damping which is desirable in various situations can be switched on, the amount of which can be adjusted via the pressure limiting valve 16. The shut-off valve 17 can be switched on by the driver by hand via a corresponding pushbutton in the dangerous situation or can be activated automatically by an ABS / ASR system.

The embodiments described above are described as a single arrangement. However, they can also be designed as a redundant system, whereby one either has the advantage of slimmer cylinders or simply obtains a redundant system that cannot fail during driving.

Reference list

<dl id="dl0002"><dt>1</dt><dd>Slewing ring</dd><dt>1'</dt><dd>Slewing ring outer ring</dd><dt>1''</dt><dd>Inner ring</dd><dt>2</dt><dd>Hydraulic cylinder</dd><dt>2'</dt><dd>Shock absorber</dd><dt>3</dt><dd>Front end</dd><dt>4</dt><dd>Swivel or ball joint on the slewing ring</dd><dt>5, 5'</dt><dd>Swivel or ball joint on the vehicle</dd><dt>6</dt><dd>Follower</dd><dt>7</dt><dd>---</dd><dt>8</dt><dd>Center of slewing ring</dd><dt>9</dt><dd>Connecting line</dd><dt>10</dt><dd>Connection of 2, 19</dd><dt>11</dt><dd>Connection of 2, 19</dd><dt>12</dt><dd>Throttle valve</dd><dt>13</dt><dd>Throttle valve</dd><dt>14</dt><dd>check valve</dd><dt>15</dt><dd>check valve</dd><dt>16</dt><dd>Pressure relief valve</dd><dt>17</dt><dd>Shut-off valve</dd><dt>18</dt><dd>Pressure accumulator</dd><dt>19</dt><dd>Hydraulic cylinder</dd><dt>19'</dt><dd>Shock absorber</dd><dt>β</dt><dd>Kink angle</dd><dt>a</dt><dd>Radius (center of the piston pivot point)</dd><dt>H</dt><dd>Piston stroke</dd><dt>F_A</dt><dd>Driving force</dd><dt>F_V</dt><dd>Thrust on the front end</dd><dt>V_H</dt><dd>Piston stroke speed</dd><dt>M₁, M₂, M_gs.</dt><dd>Damping moments</dd><dt>V_β</dt><dd>Buckling angle speed Angle between 4-M or 4'-M and the median longitudinal plane</dd><dt>X, y</dt><dd>Coordinates of the articulation points 5, 5 'to the longitudinal median plane</dd></dl>