Technical field

[0001] The present invention relates generally to articulated vehicles and more specifically an articulated vehicle with improved drive.

Background art

[0002] The need for minerals in the world is increasing while the development of the mining industry shows that the minerals to the increasing share will be extracted from underground mines. This will lead to demands for higher transport capacity, better accessibility and improved driver environment.

[0003] The transport of material from the mines with wheeled transports is usually made up the ramp but it is also an ongoing development of new mining techniques that involve transport to the crushing will be done on a horizontal transport level and then be brought to the surface with elevators or conveyors. Here are wheeled vehicles with high capacity an interesting alternative to transport by rail, which has the disadvantage of high initial costs and low flexibility.

[0004] To meet the requirements for both rapidly increasing transport volumes, lower emission levels and improved driver environment new technical solutions are required.

[0005] Today's known technology is custom-built, all-wheel drive, articulated vehicles, manufactured by piece production or short series. The vehicles are designed for underground transports and meet statutory or local safety demands, such as require that the driver's cab is protected by approved collapse and rollover protections.

[0006] A conventional truck adapted for underground transports uses two drive shafts: one drive axle in the front frame that contains drive engine, transmission and driving compartment and a drive shaft in the rear frame carrying the load.

[0007] Normal inclination for transport ramps are about 14%. The ramps are operated either with straight sections between the 180 degree curves, or in spiral form and the road surface can be both wet and with poor friction. In order to cope with transportation conditions loaded up the ramp for articulated vehicles according to prior art all-wheel drive is required and to ensure driving torque to all drive axles the front and rear axles are mechanically connected with propeller shafts. Since the distance relative the steering joint is shorter to the front axle than to the rear axle, they will also follow different radii when driving through curves, which makes that the wheels roll various long way, which in turn leads to some slippage at any wheel to equalize the resulting torsional stresses in the drive train. These slippages and high torsional stresses in the drive train provide increased wear and reduces component life.

[0008] A further problem with prior art is the design of the drive train where drive also on the axis of the front frame is both bulky and makes the design

complicated.

[0009] Also the total height is an important parameter for underground vehicles. For a typical transport vehicle for underground operation, the drive engine and driver's compartment are positioned next to each other and in front of the front drive shaft. To keep down the overall length the transmission is also placed above the front drive shaft. This arrangement lead to that two gears must be added to the drive train, on one hand for raising the driving torque to the higher positioned transmission, and on the other hand to move down output torque from the transmission to or near the level of the drive shafts center line.

[0010] The later gear has two drive outputs: an output to the drive shaft in the front frame and an output to the drive shaft in the load frame. On the basis of available space the need for the propeller shaft between the gear and the front drive shaft also increases the distance between the steering joint and the drive shaft in the front frame.

[0011] The gears require a robust design to withstand high torque in the drive system which increases the net weight and costs. The transmissions also increase the losses in the drive system, and therewith also the fuel consumption. [0012] Increased distance between the steering joint and driveshaft increases loads in the front frame due to longer moment lever and simultaneously it also has a negative impact on the vehicle's overall length, turning radius and also stability when turning.

[0013] Known transport vehicles for underground mining have as been mentioned often a design where the driver's cab and the internal combustion engine are mounted next to each other. The fact that the driver's cab and drive engine share the space limits both the size of the driver's cab and possible lines of sight and thus have a negative impact on safety and comfort.

[0014] Relatively small volumes of custom-built, customized underground machines and increasing demands for inter alia transport capacity, energy efficiency, clean exhaust and driving environment, in turn, also leads to high development costs per sold unit.

[0015] Even ordinary trucks may to some extent be used for transport in the mines. However, when using trucks, the loading capacity is a limitation and trucks are not as flexible as articulated vehicles. Additional restrictions for trucks are that the components are not designed for this type of demanding transportation with long periods at maximum power at low speeds. Also local or legal safety requirements which normally demand that the driver's cab is protected by allowed collapse and rollover protection constitute limitations.

Summary of invention

[0016] An object of the present invention is to overcome at least some of prior art problems and to provide a vehicle for underground operation, which has improved driving and handling characteristics.

[0017] According to the invention there is provided an articulated vehicle with a front part which, via a steering linkage is connected with a rear part, said front part comprises a pair of front wheels and the rear part comprises a load-carrying device and a first driven rear pair of wheels, wherein the vehicle being

characterized in that the rear part comprises a second driven rear pair of wheels arranged behind the first driven rear pair of wheels and a third driven rear pair of wheels provided behind the second driven rear pair of wheels, wherein the front pair of wheels is non-driven and two of the rear pair of wheels are steerable.

[0018] By drive on axles only of the rear part many of the above problems according to the prior art are reduced, such as torsion stresses in the drive train when steering.

[0019] In a preferred embodiment, the drive torque is transmitted from a engine provided in the front part via transmission and a propeller shaft to the first rear pair of wheels and the second rear pair of wheels.

[0020] In a preferred embodiment, the third rear pair of wheels is driven. This provides improved drive, which may be needed for transports up the ramp.

[0021] In a preferred embodiment, the third rear pair of wheels is arranged to be electrically driven by an electric drive engine, wherein an electric generator driven by a second internal combustion engine mounted in the front part and arranged to feed the electric drive engine. By that the installed power may be increased with increased transportation capacity when driving uphill.

[0022] In a preferred embodiment, the second rear pair of wheels is non- steerable and the first rear pair of wheels and the third rear pair of wheels steerable are steerable. This improves the maneuverability of the vehicle.

[0023] In a preferred embodiment, the first rear pair of wheels is non-steerable and the second rear pair of wheels and the third rear pair of wheels are steerable.

Brief description of drawings

[0024] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 shows a side view of an articulated vehicle of the invention with a front part and a rear part, whereby a driver's cab is shown demounted from a front frame of the front part; Fig. 2 shows the vehicle of Fig. 1 but with the cab mounted onto the front frame;

Fig. 3 shows a side view of the vehicle of Fig. 1 showing its drive train;

Fig. 4 shows a top plan view of the vehicle of Fig. 1 which shows the drive train; and

Fig. 5 shows the replaceable driver's cab demounted from the front frame in an alternative embodiment.

Description of embodiments

[0025] In the following, a detailed description of a preferred embodiment of an articulated vehicle according to invention will be described. This is based on an articulated vehicle with a robust underground matched load-carrying rear frame including a new solution for the propulsion system with three driving axles of the load-carrying rear frame.

[0026] In Fig. 1 an articulated vehicle, generally designated 1 is shown, comprising a front part 10, which via a steering linkage 12 is connected with a load carrying rear part 30. The front part includes a front pair of wheels, of which the left wheel 14 is shown in the figure. The front pair of wheels being interconnected by a front wheel axle (not shown in Fig. 1), which is a non-driven axle. Further, the front part 10 comprises a front frame adapted for mounting of a driver's cab 8. The front frame comprises two sections: a rear section 16a which substantially coincides with the front pair of wheels, and a front section 16b which is adapted to carry a cab. The front section 16b is thus prepared to switch cab and drive systems in relatively short time by means of an exchange system.

[0027] The driver's cab 18 is a modified front part of a truck or similar series built vehicle, comprising drive and peripheral systems, such as a drive unit in the form of an internal combustion engine 20 and a transmission 22. Therefore, in the following the term "driver's cab" will refer to a part which, beyond the drive's cab itself, also may include other components which are to be found in the front part of a truck or equivalent series built vehicles, such as the engine, transmission and climate control device. [0028] In the preferred embodiment the front part 10 also includes a protective roof 24 set up to protect the driver's cab 18 in the event of collapse. This protective roof is designed to meet the requirements for protection against falling rocks and rollover: ROPS and FOPS.

[0029] The rear part 30 has a rear frame in the form of a load frame 32. This is supported by three driven shafts with a respective rear pair of wheels, of which Fig. 1 shows the left wheel of the first, second and third rear pair of wheels, respectively, which wheels are designated 34, 36 and 38, respectively. Three driven axles provide adequate rear drive axle load relative to the total weight to push the vehicle even on steep inclines.

[0030] A load-carrying device in the form of a preferably backward tilting or sidewards tilting platform 40 is provided on the rear frame 32.

[0031] In FIG. 2, the driver's cab 18 is mounted on the front section 16b of the front frame. In this embodiment, the front section 16b of the front frame is provided with mounting planes on which the frame sides 23 on the driver's cab are mounted. This mounting is preferably done by means of bolt connections.

[0032] The drive train of the vehicle 1 will now be described in detail with reference to Figs. 3 and 4.

[0033] The drive torque from the internal combustions engine 20 is transmitted through the transmission and propeller shaft 42 to the two front drive axles of the rear drive axles, i.e. the first rear drive shaft 34" and the second rear drive shaft 36". The rear drive shaft that is at the back of the direction of travel, i.e. the third rear drive shaft 38" is driven electrically of an additional drive unit with an electric drive engine 44 and is fed by an electric generator 46 driven by an internal combustion engine mounted in the front part 10. The electric drive engine 44 and the electric generator 46 are interconnected by electrical wires (not shown). The solution provides the ability to expand the installed power and hence also the transport velocity loaded up the ramp. However, the vehicle 1 is designed for both horizontal transport and ramp transport. During horizontal transport where the power demand is lower, the electronic drive engine 44 is deactivated, i.e. the electrical supply from the generator 46 may be cancelled, and the drive of the vehicle 1 is made completely mechanically by the two front drive shafts 34 ", 36" in the rear part 30. Alternatively, the electric drive system may be completely omitted from the design.

[0034] By the rear drive shafts two shafts are controllable in relation to the rear frame 32 to reduce the turning radius. The control system for the drive shafts reads the angle of the steering joint 12 between the front 10 and rear part 30 by means of a sensor (not shown) and angles the steerable wheels in proportion to the steering angle of the steering joint. One of the rear drive axles is non- steerable. In the illustrated embodiment, the second rear drive shaft 36" is non- steerable and the first rear drive shaft 34" and the third rear drive shaft 38" is steerable, but in an alternative embodiment, not shown, the first rear drive axle 34" is non-steerable and the second 36" and third 38" rear drive axles are steerable.

[0035] The drive system of the mechanically driven drive shafts 34", 36" has longitudinal and transversal differentials 48, 50 to equalize the speed differences that arise when driving in a curve.

[0036] The non-driven shaft 14" in the front part 10 is adapted to allow passage of the propeller shaft from the transmission 42 directly to the drive shafts in the rear frame. Further, the non-driven axle 14" in the front part 10 is provided with a gas hydraulic suspension system.

[0037] The mounting plane of the drive's cab 18 in the front section 16b of the front frame is designed so that the drive train center line becomes horizontal or substantially horizontal. This prevents misalignment in the drive train, which in turn induces vibrations that shorten life spans and increases maintenance costs.

[0038] In the described vehicle a propeller shaft drive is used directly from the transmission to the first driven shaft. The distance between the steering linkage 12 and the axle of the front frame may be shortened considerably by avoiding the need for bulky extra gear required for front wheel drive. This in turn means that the bending stresses in the front frame is reduced and thus the structure's own weight is reduced. The placement of the front axle closer to the steering linkage also reduces the turning radius and improves stability when turned vehicle.

[0039] The drive axles 34", 36" and 38" in the rear part 30 are resiliently mounted to the rear frame 32 in two separate circuits: the left and right circuit, via hydraulic cylinders. The cylinders in the separate circuits are hydraulically connected to each other according to the principle of communicating vessels.

[0040] In Fig. 5, an alternative embodiment of a vehicle according to the invention is shown, in which the same parts are given the same reference numerals as in the first embodiment. The difference from the first embodiment is that the front section 16b of the custom-made bearing front frame is disassembled. Instead of being integrated with the front part 10 is thus the front section 16b of the front frame integrated to the driver's cab 18. Since both the tank for fuel and hydraulics are mounted in the front section 16b, i.e. to the partially removable driver's cab 18, the drive system may be test driven before assembly, which is an advantage.

[0041] Preferred embodiments of an articulated vehicle according to the invention has been described. It will be appreciated that these may be varied within the scope of the claims without departing from the inventive idea. For example, the transmission may be replaced by a generator which then drives a second electric engine that drives two of the drive shafts. Alternatively an electric engine mounted on each of the three drive shafts are driven by a single generator. A further alternative is that the internal combustion engine is omitted and the effect that this supply is replaced with effect from a trolley line.

[0042] Alternatively, the articulated vehicle 1 may include a front part 10 which, via a steering linkage 12 is connected to a rear part 30, wherein the front part comprises a front pair of wheels 14, 14' and the rear part comprises a load- carrying device 32 and a first driven rear pair of wheel 34, 34', the front part 10 comprises a driver's cab 18 and a drive unit 20 provided on a front frame 16a, 16b; 16a', 16b', wherein the front wheel pair 14, 14' is non-driven and the driver's cab 18 including the drive unit 20 is releasably secured to the front part 10. The driver's cab 18 comprises a front part of a series built vehicle, preferably a truck. Preferably the driver's cab 18 comprises the drive unit. Preferably, the drive unit 20 comprises an engine 20 and a transmission 22 arranged to be connected to the rear part 30. Preferably, the articulated vehicle 1 comprises a propeller drive directly from the transmission 22 to the first driven pair of wheel 34, 34 '.

Preferably, a front section 16b of the front frame is provided with mounting plane to which the frame sides 23 of the driver's cab 18 is adapted to be mounted. The frame sides 23 are preferably adapted to be mounted to the mounting planes with the aid of bolted connections. Preferably, a front section 16b of the front frame 16' is integrated to the driver's cab 18. Preferably both a tank for fuel and a tank for hydraulic is mounted to the driver's cab 18.