ARTICULATED WORKING MACHINE VEHICLE

Abstract

A working machine vehicle provided with a supporting frame and a pivoted load container, wherein the vehicle is configured to allow tilting of the load container from a transport position to a tilted position for dumping of a load from the load container, wherein the vehicle is provided with a suspension arrangement configured to reduce transfer of vibrations between the frame and the load container when the load container is in its transport position, wherein the suspension arrangement comprises a spring element and a damper element, and wherein the vehicle further is provided with at least one hydraulic hoist cylinder connected between the frame and the load container arranged to lift and tilt the load container to the tilting position for dumping.

Claims

1. A working machine vehicle provided with a supporting frame and a pivoted load container, wherein the vehicle is configured to allow tilting of the load container from a transport position to a tilted position for dumping of a load from the load container, wherein the vehicle is provided with a suspension arrangement configured to reduce transfer of vibrations between the frame and the load container when the load container is in its transport position, wherein the suspension arrangement comprises a spring element and a damper element, wherein the vehicle further is provided with at least one hydraulic hoist cylinder connected between the frame and the load container and arranged to lift and tilt the load container to the tilting position for dumping, wherein the hydraulic hoist cylinder forms part of a hydraulic system comprising a container for hydraulic fluid and at least one conduit that connects the hydraulic hoist cylinder with the container so as to form a flow passage for hydraulic fluid between the hydraulic hoist cylinder and the hydraulic container, and wherein the flow passage is arranged to exert a flow resistance to a hydraulic fluid flowing through the flow passage so as to dampen an oscillating flow through the flow passage and thereby form the damper element of the suspension arrangement.

2. The vehicle of claim 1, wherein the hydraulic container is a closed accumulator partly filled with gas so as to function as a spring for an oscillating flow of hydraulic fluid and thereby form the spring element of the suspension arrangement.

3. The vehicle of claim 1, wherein the hydraulic container is an open tank, wherein a first conduit connects the open tank with a piston side chamber of the hydraulic hoist cylinder, wherein a second conduit connects the open tank with a piston rod side chamber of the hydraulic hoist cylinder, wherein the hydraulic hoist cylinder is configured to be set in a floating state in which the hydraulic fluid can flow through the hydraulic hoist cylinder between the piston side chamber and the piston rod side chamber, and wherein the flow passage for hydraulic fluid forms a loop comprising the open tank, the first conduit, the hydraulic hoist cylinder and the second conduit, through which loop the hydraulic fluid can flow in either direction so as to form the damper element of the suspension arrangement.

4. The vehicle of claim 1, wherein the flow passage for hydraulic fluid is provided with at least one orifice to increase flow resistance to a suitable level.

5. The vehicle of claim 1, wherein the suspension arrangement comprises a spring element in the form of at least one mechanical spring.

6. The vehicle of claim 1, wherein the suspension arrangement is configured to split up a natural vibration frequency of the vehicle.

7. The vehicle of claim 6, wherein the natural vibration frequency is “f” and wherein a spring stiffness of the spring element is such that when expressed as a rotational stiffness “k” around a load container hinge, the spring stiffness satisfies the following expression:
k=(2πf).sup.2(I.sub.0+mr.sup.2)+mgr sin(α.sub.0+α) where k: Rotational stiffness around body (load container) hinge. f: Frequency of interest to prevent. I.sub.0: Moment of inertia around c.o.g. (center of gravity) of body. m: Mass of empty body. r: Distance from body hinge to c.o.g. of body. g: Gravitational constant. α.sub.0: Angle lowered body to body c.o.g. α: Angle lowered body c.o.g. to body c.o.g. in static equilibrium, supported by spring(s).

8. The vehicle of claim 1, wherein the spring element is configured to keep an empty load container at some distance above a supporting surface of the frame when the load container is set in its transporting position.

9. The vehicle of claim 1, wherein the hydraulic hoist cylinder comprises a piston, a piston rod, a piston side chamber and a piston rod side chamber.

10. The vehicle of claim 1, wherein the vehicle is provided with two hydraulic hoist cylinders, one on each side of the load container.

11. The vehicle of claim 1, wherein the vehicle is an articulated working machine vehicle, such as an articulated hauler, comprising a front vehicle section and a rear vehicle section pivotally connected via a connection arrangement configured to control a pivot angle between the front and the rear sections steering of the vehicle.

12. The vehicle of claim 11, wherein the supporting frame and the pivoted load container are arranged on the rear vehicle section.

13. The vehicle of claim 12, wherein the suspension arrangement is configured to split up a natural vibration frequency of the rear vehicle section.

14. The vehicle of claim 13, wherein the natural vibration frequency of the rear vehicle section is “f” and wherein a spring stiffness of the spring element is such that when expressed as a rotational stiffness “k” around a load container hinge, the spring stiffness satisfies the following expression:
k=(2πf).sup.2(I.sub.0+mr.sup.2)+mgr sin(α.sub.0+α) where k: Rotational stiffness around body (load container) hinge. f: Frequency of interest to prevent. I.sub.0: Moment of inertia around c.o.g. (center of gravity) of body. m: Mass of empty body. r: Distance from body hinge to c.o.g. of body. g: Gravitational constant. α.sub.0: Angle lowered body to body c.o.g. α: Angle lowered body c.o.g. to body c.o.g. in static equilibrium, supported by spring(s).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0046] In the drawings:

[0047] FIG. 1 shows an articulated hauler provided with a schematically depicted first embodiment of a suspension arrangement according to this disclosure.

[0048] FIG. 2 shows an articulated hauler provided with a schematically depicted second embodiment of a suspension arrangement according to this disclosure.

[0049] FIG. 3 shows a schematic view of a load container and some parameters used to calculate a suitable rotational stiffness.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0050] FIG. 1 shows a working machine vehicle in the form of an articulated hauler 1. The vehicle 1 comprises a front vehicle section 2 (front unit) and a rear vehicle section 3 (load unit) pivotally connected via a connection arrangement 4 configured to control a pivot angle between the front and rear sections 2, 3 for steering of the vehicle 1. The rear vehicle section 3 is provided with a supporting frame 6 and a pivoted load container 5 (body). The vehicle 1 is configured, by means of a pair of hydraulic hoist cylinders 9 (one on each side of the load container 5), to allow tilting of the load container 5 from a transport position (as shown in FIG. 1) to a tilted position for dumping of a load from the load container 5. A drivers cab is arranged on the front vehicle section 2. One pair of wheels 7 is arranged on the front vehicle section 2 and two pair of wheels 8 on the rear section 3. The vehicle 1 further comprises hydraulic systems for e.g. controlling the pivot angle and steer the vehicle and for extending the hoist cylinders 9 for dumping.

[0051] FIG. 1 shows further that the vehicle 1 is provided with a first example of a suspension arrangement 20 configured to reduce transfer of vibrations between the frame 6 and the load container 5 when the load container 5 is in its transport position. It should be noted that the suspension system 20 is only schematically depicted in FIG. 1.

[0052] The suspension arrangement 20 comprises a spring element and a damper element and is in this example a fully hydraulic system comprising the hydraulic hoist cylinders 9, a container for hydraulic fluid in the form of a closed accumulator 11 partly filled with gas 11b and a conduit 10 that connects a piston side chamber 9a (i.e. high-pressure side) of the hydraulic hoist cylinder 9 with the accumulator 11. The conduit 10 thus forms a flow passage for hydraulic fluid between the piston side chamber 9a of the hydraulic hoist cylinder 9 and the accumulator 11. The flow passage/conduit 10 is provided with an orifice 12 to increase flow resistance to a hydraulic fluid flowing through the flow passage 10.

[0053] Although not visible in FIG. 1, the (empty) load container 5 is set in a “ride”-position where the load container 5 is in its transport position but positioned a small distance from a supporting surface of the frame 6 to allow vibrational movements both upwards and downwards in relation to the frame 6.

[0054] When the load container 5 moves (vibrates) in relation to the frame 6, hydraulic fluid is forced to flow through the flow passage/conduit 10 and because of the flow resistance provided by the orifice 12 the movement (the vibrations) are dampened. In this case the hydraulic fluid flows through the flow passage/conduit 10 back and forth in an oscillating manner when the load container 5 vibrates in relation to the frame 6.

[0055] Because the hydraulic accumulator 11 is a closed container partly filled with gas 11b, and partly with hydraulic fluid 11a, and because gas can be compressed and then expand, the accumulator 11 functions as a spring for the oscillating flow of hydraulic fluid and thereby forms the spring element of the suspension arrangement 20.

[0056] FIG. 1 also shows an open tank 12 and a further conduit 13 that connects the open tank 12 with a piston rod side chamber 9b of the hoist cylinder 9. The open tank 12 functions as a reservoir for hydraulic fluid during normal hoisting operation of the hydraulic hoist cylinders 109. A still further conduit (not shown) connects the open tank 12 with the piston side chamber 9a of the cylinder 109.

[0057] FIG. 2 shows a vehicle 1 similar to the vehicle of FIG. 1 but in this case the vehicle 1 is provided with a second example of a suspension arrangement 120 configured to reduce transfer of vibrations between the frame 6 and the load container 5 when the load container 5 is in its transport position, and in particular when set in its “ride”-position similar to what is described in relation to FIG. 1. It should be noted also in the example shown in FIG. 2 that the suspension system 120 is only schematically depicted.

[0058] As shown in FIG. 2, the hydraulic container is now an open tank 112. A first conduit 110 connects the open tank 112 with the piston side chamber 109a of the hydraulic hoist cylinder 109 and a second conduit 113 connects the open tank 112 with the piston rod side chamber 109b of the hydraulic hoist cylinder 109. The hydraulic hoist cylinder 109 is configured to be set in a floating state in which the hydraulic fluid can flow through the hydraulic hoist cylinder 109 between the piston side chamber 109a and the piston rod side chamber 109b. The flow restricted flow passage for hydraulic fluid forms thus in this example a loop comprising the open tank 112, the first conduit 110, the hydraulic hoist cylinder 109 and the second conduit 113, through which loop the hydraulic fluid can flow in either direction so as to form the damper element of the suspension arrangement 120. The flow restriction is in this case generated by flow friction for the hydraulic fluid when it flows through the hoist cylinder 109. If this flow friction is not sufficient for the damping effect desired, an orifice (not shown in FIG. 2) may be arranged between tank 112 and cylinder 109.

[0059] When the load container 5 vibrates in relation to the frame 6, hydraulic fluid is also in this case forced to flow back and forth in an oscillating manner through the flow passage loop to and from the tank 112 and because of the flow resistance provided by friction (or an orifice) the vibrations are dampened.

[0060] FIG. 2 further shows that the second example of the suspension arrangement 120 comprises a spring element in the form of at least one mechanical spring 115 arranged between the frame 6 and the load container 5.

[0061] In the examples above the hydraulic hoist cylinder 9, 109 as such is of a conventional type where the piston rod is connected to the piston and where the piston is movable back on forth inside the cylinder.

[0062] FIG. 3 shows a schematic view of the load container 5, the frame 6, a load container hinge 22, and some parameters, namely center of gravity 23 (c.o.g.) at different angels α, used to calculate a suitable rotational stiffness “k” around the load container/body hinge 22. It should be noted that FIG. 3 is only schematic so the c.o.g. 23 is not correctly indicated in FIG. 3 (it should typically be more to the left in FIG. 3).

[0063] Each of the suspension arrangements 20, 120 is configured to split up a natural vibration frequency of the rear vehicle section 3. This is done by selecting the spring stiffness k so that the body eigen frequency corresponds to the frequency desired to split up and damp out, i.e. for instance the frequency 2 Hz (see also further explanations above). The spring stiffness is in this example obtained from:

k=(2πf).sup.2(I.sub.0+mr.sup.2)+mgr sin(α.sub.0+α) [0064] where [0065] k: Rotational stiffness around body (load container) hinge 22. [0066] f: Frequency of interest to prevent. [0067] I.sub.0: Moment of inertia around c.o.g. 23 of body 5. [0068] m: Mass of empty body 5. [0069] r: Distance from body hinge 22 to c.o.g. 23 of body 5. [0070] g: Gravitational constant. [0071] α.sub.0: Angle lowered body 5 to body c.o.g. 23 [0072] α: Angle lowered body c.o.g. to body c.o.g. in static equilibrium, supported by spring(s).

[0073] Since it is possible to use both a mechanical spring, typically arranged at a front edge of the body/load container, and a gas spring (hydraulic accumulator), it is convenient to express the spring stiffness as a rotational stiffness around the body hinge. For articulated haulers of the type exemplified in FIGS. 1 and 2 the rotational stiffness k is around 110 kNm/deg.

[0074] A relative damping (damping ratio) of around 0.3-0.4 for the spring suspended body 5 is suitable for articulated haulers of the type exemplified in FIGS. 1 and 2. The damping may be calculated from:

c=ζ2Iω.sub.n [0075] where [0076] c: Damping of system. [0077] ζ: Damping ratio. [0078] I: Moment of inertia of body 5 around body hinge 22. [0079] ω.sub.n: Natural frequency of suspended body 5.

[0080] A damping magnitude of around 350 kNs/m is suitable for the examples described here.

[0081] The hydraulic parts of the suspension arrangements 20, 120 may in practice be arranged in different ways and be located at various places on board the vehicle.

[0082] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.