GB2104010A

GB2104010A - >Tyre testing apparatus

Info

Publication number: GB2104010A
Application number: GB08125466A
Authority: GB
Inventors: Denis James Howells
Original assignee: FROUDE ENG Ltd
Current assignee: FROUDE ENG Ltd
Priority date: 1981-08-20
Filing date: 1981-08-20
Publication date: 1983-03-02

Abstract

An apparatus for testing, e.g. measuring rolling resistance of, a pneumatic tyre comprises a rotatable drum 13, a first frame 24 connected to a pedestal 23 and to trunnions on the drum shaft so as to be pivotable about a first horizontal, axis extending radially of the drum by means of hydraulic actuators 30, 31, a second frame 32 connected to parts 24b and d of the first frame so as to be pivotable about a second axis by means of an hydraulic actuator 35, and a carriage which rotatably mounts a tyre 41 to be tested and is slidable in the frame 32 by means of an hydraulic actuator 42 to urge the tyre against the drum. The pivotal axes of the frames 24, 32 intersect each other at the point of contact of the drum with the centre of the tyre tread, and pivoting of the frames 24, 32 enables the slip and camber angles of the tyre to be altered. <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatuses for measuring rolling resistance and/or other forces and/or moments The present invention relates to an apparatus for measuring rolling resistance and/or other forces and/or moments. Such an apparatus may be used in the testing of pneumatic tyres for road vehicles.

According to one aspect of the invention, there is provided an apparatus for measuring rolling resistance and/or other forces and/or moments, comprising a base, a drum rotatably mounted on the base, a first frame pivotably mounted with respect to the base, first means for pivoting the first frame with respect to the base, a second frame pivotably mounted on the first frame, second means for pivoting the second frame with respect to the first frame, and a carriage movably mounted in the second frame and arranged to be urged towards the drum, the carriage including measuring means and means for mounting a tyre with the axially central radial plane in a predetermined position, the pivotal axis of the first frame extending radially of the drum and passing through the point of contact of a tyre to be tested at the axially central radial plane thereof with the drum.

Preferably, the first frame is pivotably mounted to a trunnion which is rotatably mounted on the drum axle.

According to another aspect of the invention, there is provided an apparatus for measuring rolling resistance and/or other forces and/or moments, comprising a rotatable drum, a carriage for mounting a tyre to be tested, and a gimbal mounting supporting the carriage with respect to the drum, the axis of the gimbal mounting intersecting at the point of contact of the drum with the tyre and one of the gimbal axes extending radially with respect to the drum.

The invention will be further described, by way of example, with respect to the accompanying drawings, in which: Figure 1 is a perspective view of a rolling resistance measuring machine constituting a preferred embodiment of the invention; Figure 2 is a part-sectional side view of the machine of Figure 1; Figure 3 shows a fragmentary section on the line A-A of Figure 2; and Figure 4 shows a cross-section on the line B-B of Figure 3.

The rolling resistance measuring machine comprises a base frame 1 fabricated from rectangular section metal and supported on a floor by means of four-anti-vibration feet 2. At one end of the frame 1 , there is provided a vertical structure comprising members 3, 4, 5, 6, 7, 8 and 9. A shaft 10 is rotatably mounted in the member 9 by means of two deep groove ball bearings 11 and 1 2 which resist radial and axial loads on the shaft. A drum 13 is fixed coaxially to one end of the shaft 10 and is coated on its outer curved surface with a fine grain abrasive compnund. The other end of the shaft is fixed to a toothed wheel 14 and a brake disc 1 5.A pair of diagonally opposite pneumatic caliper brakes 1 6 are fixed to the members 3 and 4 and cooperate with the disc 1 5 for decelerating the drum 1 3.

The members 5, 6, 7, 8 extend above the shaft 10 and are connected together at their top ends by a platform 1 7. A plate 1 8 is pivotably mounted to the platform 1 7 and provided with an adjusting device 1 9. A variable speed thyristor controlled DC electric motor 20, which is also capable of providing regenerative braking, is mounted on the plate 1 8. The output shaft of the motor 20 is provided with another toothed wheel 21 which is connected to the toothed wheel 1 4 by means of a toothed belt 22. The adjusting device 1 9 permits the tension of the belt to be adjusted to a suitable value.The toothed belt 22 and the toothed wheel 14 and 21 provide a reduction drive from the electric motor 20 to the shaft 10 and drum 13.

At the end of the base 1 opposite the vertical structure, there is provided a pedestal 23 extending upwardly from the base frame 1. A first frame or cradle 24 comprising rectangular section members 24a-o is pivotally fixed at the free end of the member 24m to the top of the pedestal 23.

The members 24n and 240 extend parallel to each other and are interconnected by a further member 24p or rectangular section. The free ends of the members 24n and 240 are pivotally connected by means of bearings 25 and 26 to the trunnions of a gimbal type trunnion member 27 which is rotatably mounted on the end of the shaft 10 by means of two ball bearings 28 and 29. The cradle 24 is thus pivoted about a horizontal axis which extends radially of the drum 1 3 through the axis of the shaft 10 and in the axially central radial plane of the drum 1 3.Two servo-operated hydraulic actuators 30 and 31 are connected between opposite sides of the base frame 1 and the members 24c and 24a of the cradle 24 so as to allow the cradle to be pivoted about its axis by it 50 about a central position in which the members 24a, 24n, and 240 are horizontal.

A second frame or cradle 32 comprises rectangular section members 32a-32f formed into a U-shaped part comprising members 32a, b, c and a rectangular part comprising members 32d, 32e, 32f, and part of 32b and extending perpendicularly to the U-shaped part. The free ends of the members 32a and 32b are connected to the first cradle 24 by means of bearings 33 and 34 so that the second cradle is pivotable by +5 about an axis which intersects the pivotal axis of the first cradle 24 perpendicularly and which is tangential to the curved surface of the drum 13.A servo-operated hydraulic actuator 35 is connected between the first and second cradles for pivoting the second cradle 32 with respect to the first cradle 33 about the said axis, the median pivotal position of the second cradle 32 being such that the rectangular part thereof lies in a radial plane with respect to the shaft 10.

A load carriage 36 is slidable in linear roller bearings in the rectangular part of the second cradle 32 so as to be movable radially with respect to the shaft 10. The load carriage 36 carries a stub-shaft which is rotatable in antifriction bearings provided in a multi-component wheel dynamometer 38 which provides signals indicative of longitudinal, lateral, and vertical forces and moments. The wheel dynamometer is rigidly bolted to the carriage 36 and the stub-shaft rotates in the dynamometer. The end of the shaft 37 is flanged at 39 and provided with threaded holes so that a test wheel 40 and tyre to be tested can be fixed to the dynamometer. Figure 4 shows at 41a and 41 b two different cross-sections of tyres with different rim sizes of the wheel 40 to give an indication of the range of tyre sizes which may be accommodated.The carriage 36 is connected to a servo-operated hydraulic actuator 42 which is also connected to the second cradle 32 and urges the carriage toward the drum 13 so as to press the tread of the tyre against the outer surface of the drum 13 with a predetermined loading. The other end of the shaft 37 is fitted with a slip-ring assembly and a rotary union. The slipring assembly is used to facilitate the measurement of temperatures from suitable probes inserted into the tyre, whereas the rotary union facilitates supply of compressed air to the tyre and the measurement of pressure. An adaptor 43 is screwed into the first end of the shaft 37 and is connected via a flexible connection 44 to the valve of the tyre being tested. A hole drilled through the shaft connects the adaptor to the rotary union.

A selection of wheels 40 are provided with different rim sizes so as to accommodate tyres of different sizes and profiles. The wheels are arranged so that, when attached to the flange 39, the axially central radial plane of the tyre tread is coplanar with the axially central radial plane of the drum 1 3. Thus, if the tyre 41 is considered to make a line contact with the surface of the drum 13, then the centre of the line of contact coincides with the intersection of the pivotal axes of the first cradle 24 and the second cradle 32 on the surface of the drum 13. With the cradles 24 and 32 at their median pivotal positions, the rotary axis of the tyre is parallel to the axis of the drum 13.As mentioned above, the second cradle 32 can be pivoted by means of the actuator 35 so as to vary the camber angle of the tyre 41 with respect to the drum 13 by +, for example,5 . The first cradle 24 can be pivoted by the actuators 30 and 31 so as to steer the tyre to provide a slip angle with respect to the drum 1 3 which can be varied within the range +15 .

In use, the hydraulic actuators 30, 31,35, and 42 are connected to a hydraulic power pack (not shown), for instance comprising an oil storage tank, an oil cooler, and pumps with pipe connections to suitable manifold plates from which the connections to the actuators are provided by flexible piping. The caliper brakes 1 6 are connected to a suitable pneumatic power supply and the motor 20 is connected to a variable speed thyristor control power unit. A tyre 41 to be tested is mounted on the appropriate wheel 40, which is fixed to the flange 39 of the shaft 37. The wheel dynamometer is connected to apparatus for measuring and analysing data concerning testing of the tyre.

The motor 20 drives the shaft 10 via the toothed belt 22 so as to rotate the drum 13. The actuator 42 is operated so as to provide a predetermined force or pressure of the tyre 41 against the surface of the drum 13. The actuators 30, 31, and 35 are then operated so as to provide various castor and slip or steering angles to the wheel and tyre while the measurements obtained from the wheel dynamometer are stored and/or analysed to provide information concerning, for instance, the rolling resistance of the tyre.

Because the pivotal axes of both the first and second cradles 24 and 32 pass through the centre of the line of contact of the tyre 41 on the drum 1 3, the camber and slip angles of the tyre can be changed without substantially affecting the accuracy of the measurements provided by the wheel dynamometer 38. In particular, substantially no sources or moments are created on the wheel as a result of variations in the camber and slip angles, in contrast with known machines used for testing tyres and the like. Thus, the accuracy of measurement of the present machine is substantially improved with respect to the known machines. Further, the force urging the tyre 41 against the drum 1 3 reacts, via the first and second cradles, on the shaft 10 to which the drum 1 3 is rigidly connected. Thus, any distortion introduced by this force can be reduced to essentially as low a level as desired merely by providing the first and second cradles with the appropriate strength and rigidity. Again, this improves the accuracy of the present machine with respect to known machines, in which the relative force between the tyre and drum acted through various frames mounted on a base and could thus cause undesirable deflections in the relative orientations of the drum and tyre.

Claims

1. An apparatus for measuring rolling resistance and/or other forces and/or moments, comprising a rotatable drum, a carriage for mounting a tyre to be tested, and a gimbal mounting supporting the carriage with respect to the drum, the axes of the gimbal mounting intersecting at the point of contact of the drum with the tyre and one of the gimbal axes extending radially with respect to the drum.

2. An apparatus for measuring rolling resistance and/or other forces and/or moments, comprising a base, a drum rotatably mounted on the base, a first frame pivotably mounted with respect to the base, first means for pivoting the first frame with respect to the base, a second frame pivotably mounted on the first frame, second means for pivoting the second frame with respect to the first frame, and a carriage movably mounted in the second frame and arranged to be urged towards the drum, the carriage including measuring means and means for mounting a tyre with the axially central radial plane in a predetermined position, the pivotal axis of the first frame extending radially of the drum and passing through the point of contact of a tyre to be tested at the axially central radial plane thereof with the drum.

3.An apparatus as claimed in claim 2, in which the first frame is pivotably mounted to a trunnion which is rotatably mounted on the drum axle.

4. An apparatus for measuring rolling resistance and/or other forces and/or moments, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.