Disc Brake for a Vehicle and Vehicle comprising a Disc Brake

TECHNICAL FIELD

The invention relates to a disc brake and vehicle comprising a vehicle according to the preambles of the independent claims.

BACKGROUND OF THE INVENTION

Work machines are vehicles designed for and used in rough off-road surroundings where trucks or passenger cars are inoperative and would be damaged when exposed to these rough conditions.

In order to allow a good off-road performance and a sufficient ability to successfully handle slippery conditions a work machine requires a reliable brake system. It is known in the art to use disk brakes of the type with e.g. a floating or a fixed calliper. In a disk brake a disk is rotating with the wheel. While braking, two friction pads arranged in a U-shaped calliper are pressed against the disk, one from the inside, one from the outside. The calliper is connected with the wheel suspension and does not rotate with the wheel.

The friction pads are in principle kept in place by arranging the friction pads to be urged towards a pin or a lock heel. There are also solution known in the art where friction pads are mounted between casted heels but a prerequisite is that the calliper is radially open which is not acceptable for work machines due to the rough working ambient of work machines.

In US 4,061 ,209 A1 a vehicular disk brake with a floating calliper is disclosed which is slidably mounted on a carrier which is fixed to the vehicle. An actuator urges a first friction pad onto one side of a rotatable disc to cause the calliper to slide relative to the carrier and apply a second friction pad to the other side of the

rotatable disc. The sliding connection is provided by a pair of pins slidable in recesses in one of the calliper or the carrier and releasably secured to the other component, i.e. the carrier or the calliper. To prevent binding of the pins in their recesses, at least one recess is made diametrically oversized and the associated pin is urged into an eccentric position in direct sliding contact with the wall of its recess by means of a leaf spring which also resiliently urges the friction pads into position in the carrier. When both pins extend into radially oversized recesses, they are relieved of drag forces which arise on brake forces

In a work machine, such as e.g. an articulated hauler, it is desirable to provide a high brake torque. The higher the brake torque, however, the higher is the mechanical stress in the calliper, particularly in areas where the friction pads are attached to the calliper.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a disc brake which allows for high brake torques without overloading the calliper with mechanical stress. Another object is to provide a vehicle with an improved disc brake.

The objects are achieved by the features of the independent claims. The other claims and the description disclose advantageous embodiments of the invention.

According to a first aspect of the invention, a disk brake for a vehicle being connectable to a vehicle frame is proposed, comprising a calliper mounted slidably in respect to the vehicle frame, and at least one pair of friction pads which is attached to the calliper on either side of a rotatable disc, wherein each friction pad provides at least one recess with which a pin engages which is attached to the calliper. The recess is formed as an oval or elliptical or an oblong opening with an outer edge proximate to the outer side of the friction pad and an inner edge wherein a longer centreline between the inner and outer edges of the recess extends in the rotation direction of the rotatable disc.

Favourably, the cross section of the recess allows to redirecting the force generated between the pin and the circumference of the recess when the friction pad is in contact with the rotating disc and the pin is in contact with the recess circumference in a way that it is possible to absorb the reaction forces generated by higher brake torques compared to conventional attachments of the friction pad. This is particularly advantageous in cases where the friction pads are heavily worn as this creates a high torque on the attachment pins due to the fact that the reaction force will act at a relatively long lever distance in the friction pad locking position with the one or more pins locked in the one or more recesses. In contradistinction to this a compressive force is generated towards the attachment pins in the calliper in the prior art solutions. Favourably, the free space for both pins in the recesses is always directed to the radial inner side of the friction pads. The oval or oblong circumferences of the recesses provide a control surface which "guides" the friction pad relative to the pin. This is enhanced by the fact that the difference in diameter between the recess in the friction pad and the pin is small according to the invention, whereas in the prior art with oversized openings surrounding the pins, there is always a clearance between pin and opening in the friction pad.

Advantageously, by means of locking the friction pads in the proposed way, instead of creating a compression force on the attachment pins at the inner side of the calliper when the friction pads are in an operative state generating a brake torque, a tensile force is generated.

Preferably, the friction pad in an area around the recess can exert a tensile force on the pin. There would be a very high tensile stress on the inner side of the calliper with a locking principle of the friction pads where the friction pads exerts a compressive force in the attachment pins, especially at high brake torques in combination with worn friction pads. Advantageously, there is always a gap between the pin and the recess located at the inner side of the recess, i.e. also at the inner side of the calliper. This enables that there is always a tensile stress on the calliper outside and compressive stress on the inner side of the calliper.

The pin assigned to the respective recess can be arranged in the outer edge of the recess when the friction pads are in an inoperative state. This allows for a symmetric arrangement so that the favourable tensile forces on the pins can be generated independently from the rotation direction of the rotatable disc, i.e. the rotation direction of the wheel.

Advantageously, in an operative state the outer edge of the recess upstream of the rotation direction is urged against the pin assigned to the respective recess when the friction pads are pressed against the rotatable disc.

Preferably, two recesses are provided in each friction pad on opposing sides of a diameter of the friction pads for operational connection with one pin for each recess.

According to another aspect of the invention, a vehicle is proposed comprising a disk brake connected to a vehicle frame, comprising a calliper mounted slidably in respect to the vehicle frame, and at least one pair of friction pads which is attached to the calliper on either side of a rotatable disc, wherein each friction pad provides at least one recess with which a pin engages which is attached to the calliper. The recess is formed as an oval or a oblong opening with an outer edge proximate to the outer side of the friction pad and an inner edge wherein a longer centreline of the recess extends in the rotation direction of the rotatable disc.

The invention can be applied to wheel-borne vehicles, track-borne vehicles and vehicles running on rails. Primarily wheel-borne vehicles are intended. The invention is particularly useful work machines, such as frame-steered articulated haulers, wheel loaders, excavators etc. The invention is particularly applicable in vehicles with a multitude of driven axles and will below be described for a frame- steered articulated hauler for the purpose of exemplification. The invention can also be applied to passenger cars, trucks, buses and other road vehicles but is primarily intended for vehicles used off-road in rough conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiment, but not restricted to the embodiment, wherein is shown:

Fig. 1 a side view of a preferred vehicle according to the invention, embodied as an articulated hauler;

Fig. 2 a side view of a preferred disc brake according to the invention;

Fig. 3 a top view of the disc brake along the cut Ill-Ill in Fig. 2; and Fig. 4a, 4b a detail of the preferred disc brake of Fig. 2 and 3 (Fig. 4a) and an elliptical recess in a friction pad (Fig. 4b) according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.

Fig. 1 shows a vehicle 10 preferably embodied as a frame-steered articulated hauler in a side view according to the invention.

The vehicle 10 embodied as a frame-steered articulated hauler comprises a front vehicle section 12 comprising a front frame 14, a front wheel axle 16 and a cab 18 for a driver. The vehicle 10 also comprises a rear vehicle section 20 comprising a rear frame 22, a front wheel axle 24, a rear wheel axle 26 and a tiltable platform body 28.

The front and rear wheel axles 24, 26 of the rear vehicle section 20 are connected to the rear frame 22 via a bogie arrangement (not shown), and will below be referred to as front bogie axle 24 and rear bogie axle 26.

Each of the front wheel axle 16, the front bogie axle 24 and the rear bogie axle 26 comprises pairwise left and right wheels 100, 102, 104. Only the left wheels 100, 102, 104 are depicted.

The front frame 14 is connected to the rear frame 22 via a first rotary joint 46 which allows the front frame 14 and the rear frame 22 to be rotated relative to one another about a vertical axis 60 for steering (turning) the vehicle 10. A pair of hydraulic cylinders 52 is arranged on respective sides of the rotary joint 46 for steering the vehicle 10. The hydraulic cylinders are controlled by the driver of the vehicle 10 via a wheel and/or a joystick (not shown).

A second rotary joint 54 is adapted in order to allow the front frame 14 and the rear frame 22 to be rotated relative to one another about an imaginary longitudinal axis, that is to say an axis which extends in the longitudinal direction of the vehicle 10.

The platform body 28 is connected to the rear frame 22 via an articulation (not shown) on a rear portion of the rear frame 22. A pair of tilting cylinders 56 is connected with a first end to the rear frame 22 and connected with a second end to the platform body 28. The tilting cylinders 56 are positioned one on each side of the central axis of the vehicle 10 embodied as a frame-steered articulated hauler in its longitudinal direction. The platform body 28 is therefore tilted in relation to the rear frame 22 on activation of the tilting cylinders 56.

Fig. 2 depicts a side view of a preferred disk brake 200 for a vehicle 10 (Fig. 1), whereas Fig. 3 illustrates the arrangement of the disc brake 200 in more detail by a top view onto the section revealed by the cut along Ill-Ill in Fig. 2. The disc brake 200 is connectable to a vehicle frame (not shown), comprising a U-shaped calliper 202 mounted slidably in respect to the vehicle frame. The calliper 202 is mounted on an upper part of a rotatable disc 220 which rotates with the wheel (not shown), wherein a front side 203 of the U-shaped calliper 202 extends on the front side of the rotatable disc 220 and the opposite rear side of the U-shaped calliper 202 extends on the rear side of the rotatable disc 220. The rotatable disc 220 can rotate in counterclockwise direction A or in clockwise direction B.

The calliper's 202 front side 203 and rear side 205 are positioned on each side of the rotatable disc 220. Both sides 203, 205 are symmetric to each other and symmetric to a centre line 222 perpendicular to the rotatable disc 220. From the left outside to the inside of the calliper 202 a pin 208a is attached with a screw 218a to the side 203 of the calliper 202. The pin 208a is flush with the outer surface of the friction pad 206 and engages with a recess 210a formed in an end piece 216a of the friction pad 206. In a non-operative state of the friction pad 206, a small gap 207 is formed between the outer surface of the friction pad 206 and the rotatable plate 220.

A ram member 204a protrudes from the side 203 of the calliper 202 towards the near side of the friction pad 206 and contacts the inner surface of the friction pad 206 opposite to the outer surface.

Being symmetrical to the centre line 222, the arrangement is likewise from the right outer side to the inside of the calliper 202. A pin 208b is attached with a screw 218b to the side 203 of the calliper 202. The pin 208b is flush with the outer surface of the friction pad 206 and engages with a recess 210b formed in an end piece 216b of the friction pad 206.

A ram member 204b protudes from the side 203 of the calliper 202 towards the near side of the friction pad 206 and contacts the inner surface of the friction pad 206 opposite to the outer surface.

When a brake torque is required, the calliper 202 is shifted adequately so that the ram members 204a and 204b press the friction pad 206 towards the rotatable disc 220.

When the rotatable disc 220 is rotating in direction A, the arrows A1 at the end pieces 216b indicate the direction of the acting force between friction pad 206 and pins 208b, and the light curved arrows in the pins 208b indicate the torque acting on each pin 208b. When the rotatable disc 220 is rotating in direction B, the arrows B1 at the end pieces 216a indicate the direction of the acting force

between friction pad 206 and pins 208a, and the light curved arrows in the pins 208a indicate the torque acting on each pin 208a.

The recesses 210a and 210b have an oval or oblong cross section. A free space 209a, 209b in the recesses 210a, 210b directs toward the inside so that the respective pin 208a, 208b is positioned in an outer edge of the recesses 210a, 210b which is shown in more detail in Fig. 4a and 4b by way of example for the pin 208b on the right hand side in Fig. 3.

The pin 208b forming the attachment of the friction pad 206 to the calliper 202 is positioned in the outer edge 212 of the recess 210b leaving an empty space 209b in the recess 210b between the pin 208b and the outer edge 214 directed to the inner direction of the friction pad 206. The recess 210b is formed as an elliptical or an oblong opening. The position of a ram member 204b is indicated by a dotted line.

Fig. 4b shows that a longer axis 211 of the recess 210b is oriented in direction of the rotation direction A - and consequently in direction B for the recess 210a - and the smaller axis 213 is directed crosswise to the rotation direction A or B. The arrow in the pin 208b indicates the torque on the pin 208b with the disc 220 rotating in direction A.

Favourably, the invention allows for applying a high brake torque even if the friction pads 206 have already experienced a high load and a high wear.