GB2371340A - Automotive running gear abrasion and/or corrosion testing - Google Patents

Abstract

To test automotive running gear 12, such as disc brakes, a non-vehicular rig (eg. a dynamometer) is provided having mounting and drive means 18-24 for the running gear together with air powered spray 38 or rotary brush means to apply doses of a liquid treatment medium 36 comprising water with optionally dispersed abrasive particles and/or a corrosion agent so that the treatment medium enters where possible between relatively movable parts of the running gear, or tests for such entry being promoted during testing of actuation of the running gear. An acid/salt/soil test solution is disclosed, and window washing/wiping may be necessary to view such mud spraying. The testing may carried out in a sequence of liquid application followed by running gear actuation. Thus failure modes identification in disc brakes and the like is accelerated by simulating extended periods of road testing, but in days rather than months.

Description

METHOD AND APPARATUS FOR BRAKE TESTING

This invention relates to a method and apparatus for brake testing and is particularly but not exclusively applicable to the testing of automotive disc brakes but may well find useful application more generally in relation to the testing of automotive running gear used in the wheel region of an automotive vehicle, where sliding and/or rotating motion of parts relative to each other occurs and such parts are likely to be subjected to repeated applications of abrasive and/or potentially- corrosive liquid and/or solid materials during the use.

Thus, for example, test work in relation to automotive disc brakes of the kind employing slidable discs and/or slidable or tiltable disc/straddLing calipers-. has shown them to be able to develop a failure mode in which (after an extended period of such testing) certain components no longer are capable of effecting the required relative movement (whether sliding or angular), or such movement is sufficiently resisted to have the result that the mechanism does not perform satisfactorily.

On-vehicle testing to achieve the result of such a degree of mechanism functional breakdown has been commonly found to require a period of some months, and such an extended period entails very substantial testing costs, as will be well understood. Nethertheless, it is highly desirable to be able to test a disc brake to the point at which such a failure mode is repeatably established in order to be able to analyse the contributions to such failure of the individual parts of the mechanism after disassembly and analysis. In this way, the intending manufacturer can establish the basis for providing a mechanism at an affective cost which will reliably provide

the required term of use under average automotive operation conditions.

Clearly however there is a considerable need for some means to accelerate such tests and/or indeed to reduce the inherent cost of such.

Existing procedures for testing brake mechanisms include dynamometer apparatus, which is well adapted to carry out extended testing under laboratory-type conditions and is indeed capable (if so designed) of carrying out extended wear tests on an exhaustive and repetitive basis so as to simulate reasonably rapidly the carrying out of exhaustive repetitive stopping tests on an automotive vehicle. However, such exhaustive wear testing does not in itself provide any anser to the requirement for a means to simulate the failure modes in brake equipment other than due to frictional wear on the braking, surfaces-. In other words, such extended and high energy dynamometer tests do not in themselves enable simulation of the failure of a brake due to the corrosive effects of wet and dry and mixed media encountered during normal automotive use.

In an attempt to remedy this deficiency, tests have been devised in which brakes are subjected to immersion in various corrosive and/or abrasive media prior to brake use in order to accelerate the occurrence of wear during the ongoing test procedure. However, such a system has been found not to be particularly effective and/or economic not least because total immersion involves the provision of a substantial bath for the purpose, not to mention the fact that in the case of a vehicular test the immersion arrangement necessarily involves the immersion of at least two of the relevant mechanisms and the provision of a bath at least somewhat larger than the vehicular width. Even in the case of a dynamometer test the use of an immersion technique would be relatively unhelpful due to the fact

that the dynamometer equipment would need to be specially designed in order to accommodate the equipment immersion bath around the driven assembly, and such would require substantial redesign.

In short, previous approaches to the technique have fallen short of the requirement to provide a means for exhaustive testing over a relatively short period but in a manner which will simulate the corrosion effects of extended road testing. One aspect of this latter requirement, we have discovered, is the intermittent nature of the test work itself. The electrochemical aspects of the corrosion process have a requirement for conditions which are best achieved in a manner which simulates or provides the intermittent wet-and-dry conditions-with at least intermittent availability of atmospheric oxygen, and such conditions need to be made ; available even to the interstices of the relatively movable parts of the brake mechanism during the test.

We have also discovered that despite the fact that the need for exhaustive testing of this kind has existed for many years and despite the fact that the individual items of equipment capable of achieving same in accordance with the principles set out below is of the kind which has itself been available for many years, means can readily be provided for carrying out exhaustive tests of the kind discussed herein in a relatively simple manner and using substantially already available equipment, and at relatively modest cost, as indeed will be seen from the specific embodiments described below.

An object of the present invention is to provide a method and apparatus applicable inter alia to the testing of disc brakes and providing improvements in relation to some at least of the criteria discussed above, and/or improvements generally in relation thereto. According to

the invention there is provided a method and apparatus as defined in the accompanying claims.

In an embodiment of the invention described below we provide a test rig wherein apparatus for non-vehicular testing of brake equipment is provided with spray means adapted to apply to brake equipment to be tested, a treatment medium comprising, at a minimum plain water, or, more usually, a dispersion or emulsion of at least one abrasive material and/or a dispersion or solution of a corrosive material. In the illustrated embodiments, the treatment medium is intermittently sprayed onto the brake structure and is caused to penetrate into the'interstices of that mechanism not only by virtue of its spray application but by virtue of intermittent actuation of the brake mechanism so as to cause relative movement of the relatively movable (whether by sliding or angular movement) structures so as to maximise the entry of the abrasive and/or corrosive medium into the'tolerance spaces between the relatively moveable parts. Alternatively, doses of the treatment medium may be applied by dosage means such as rotary brush means.

Likewise in the embodiments, the method provides tor intermittent application of the treatment medium and intermittent actuation of the brake or other mechanism, such times of treatment and actuation being interleaved with periods of quiescence (or non-actuation) therebetween, as appropriate to permit partial or complete drying out under ambient conditions, for the maximisation of corrosion and/or abrasion both during such interim periods and upon recommencing brake actuation.

In the embodiments the adoption of a spray or other dosage technique for the application, particularly of a suspension of an abrasive material such as soil or sand acidified or not, (or even plain water), enables the

making of a test in which the worst (or worse than) conditions generated during road testing (in terms of ambient conditions) are instantly and repeatably generatable in a cost-effective manner and without any significant structural modification of the test equipment whether the latter be of the dynamometer kind or otherwise.

Thus, for example, the most abrasive conditions of a vehicular test and its subsequent period of intermission (during which corrosion proceeds unabated or if anything is accelerated) can be simulated by the mere addition to dynamometer or the like apparatus of spray-application apparatus (of whatever droplet size may be judged suitable) or other dosage apparatus capable of handling a corrosive and/or abrasive treatment medium.

In this way, a most cost-effective approach to what may be termed"destructive vehicular testing"in. the laboratory/on the test rig is provided. Moreover, because

in the embodiments the dosage apparatus can be adapted to p apply doses of the treatment medium whether as droplets or otherwise, to selected portions of the running gear under test, and indeed in varying doses thereto, a degree of versatility is provided which would be extremely difficult to offer by means of road testing procedures.

Because apparatus for the application of a treatment medium by means of droplets (containing dispersed abrasive constituents and/or corrosive constituents, or even plain water) or by means of other dosage apparatus, can be simply added to a test rig of the kind involving dynamometer apparatus, so that the droplets or doses are simply directed towards the tested brake or other apparatus from a direction (usually) approximately lateral to the axis of rotation of the relevant brake wheel or other rotary device, no modification to the drive arrangements for the apparatus (or substantially none) are required. Whereas in

the case of the previously considered immersion tests there has been a need either to modify the drive and sealing arrangements to accommodate the inevitably substantial size of the liquid immersion bath, no such problem arises here.

The test rig can be constructed substantially in its usual format and layout and with its usual drive arrangements, and the treatment medium application apparatus can then be effectively bolted-on at the side, provided there is room, or else by means of some (usually minor) rearrangement of existing equipment at one lateral side of the apparatus or the other, or indeed above it.

Although plain water may be employed as the treatment medium a particular aspect of the embodiments relates to the method of provision of the treatment medium with an abrasive consistent suitably included therein. For this purpose the arrangement adopted does not seek to replicate the conditions typically arising in the case of a road test in which mud (meaning any abrasive particles which may be encountered on a roadway or adjacent surface) is effectively caused to be raised from its location on the road way or other surface by tyre impact and to be (if available) mixed with ambient roadway water and generally dispersed within the wheel arches of the vehicle on the basis of some degree of admixture with the water. In a road vehicle, measures are taken to minimise the extent to which such liquid and solid material can reach the brake structures, and the material applied may contain varying amounts of abrasive and/or corrosive materials depending on the chance physical manner in which the admixture process occurs.

For the purpose of the tests of the embodiments of the present invention described below, and with a view to ensuring that the test conditions are as adverse (for product life) as possible, the treatment medium which is

applied to the brake under test in the form of droplets or other doses, is provided as a dispersion in a suitable liquid medium (usually water) of the relatively abrasive particles (such as soil and/or sand particles) which are relatively uniformly dispersed in the liquid medium. This ensures that all droplets reaching any part of the mechanism on a direct impact basis are likely to contain at least a quantity of the abrasive material corresponding to the concentration thereof in the liquid portion of the treatment medium, overall.

By adopting an approach in which the conditions of use of the brake under test can be made significantly more disadvantageous (with respect to producing abrasion and/or corrosion) than those which would be encountered-during vehicular testing (for the reasons explained above), the embodiments of the invention are able to produce, the required accelerated testing and wear conditions very straightforwardly and this is achieved by use of relatively very simple equipment in combination with standardised test apparatus, for example of the dynamometer kind. In principle, (and indeed in practice) all that is needed in addition to such test apparatus is corresponding apparatus for the provision of a supply of suitable treatment medium (with dispersed abrasive content and/or corrosive content), and the generation of droplets of such and the direction of a spray or directed stream of such droplets towards the relevant region of the brake or other running gear under test.

In practice this latter requirement can be achieved in a variety of ways, but one particularly straightforward and effective mode of achieving this has been found to be the use of air jets not only for producing a mixing effect with respect to the dispersal of an abrasive particulate material in the liquid treatment medium but also for the

subsequent step of generating dosage in the form of a droplet spray of such medium for directional application to a brake under test. As mentioned above, such application to the brake under test is conducted at time-separated intervals with actuation of the brake occurring between and/or during such spray application in order to ensure complete penetration of the mechanism, so far as such is not prevented by seals.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawing in which there is shown a representation in side elevation of test apparatus in the form of dynamometer apparatus adapted to carry out a method according to the invention.

As shown in the drawing, apparatus 10 for-testing automotive running gear 12, which in this embodiment is in the form of a disc brake, comprises non-vehicular apparatus 14,16 to mount and drive disc brake 12 and to actuate same for testing the carrying out of its designed functions, otherwise than on an automotive vehicle.

It will be seen in the drawing that apparatus 14,16 for mounting and driving disc brake 12 comprises apparatus modules 18,20, 22 and 24 serving to mount and drive the disc brake together with a base module 26 providing support and power supply functions. The entire apparatus 10 is generally of known dynamometer apparatus construction and in this case may be termed a brake test rig, which incorporates the features described below providing an embodiment of the invention.

Running gear 12, in the form of a disc brake, is in this embodiment a disc brake of the kind described in WO 98/26192 (docket 2558) and WO 98/25804 (docket 2561) in which twin brake discs are mounted for axial sliding movement with respect to an axially fixed hub under the control of one fixed and two slidable friction elements

actuated by a hydraulic piston and cylinder assembly mounted at one side of a fixed caliper structure in which the non-fixed friction elements are slidable. It will be understood that the axially sliding movement of the discs and likewise of the friction elements are essential to the proper operation of the disc brake and such movement is of key relevance for the purposes of the present invention which seeks to simulate the production of seizure of such relatively sliding parts so that the brake is prevented from operating, and to achieve such seizure or failure without the necessity to carry out months of vehicular testing.

Brake 12 is mounted between modules 18 and 22 and directly on module 20 so that its brake discs (not shown) can be rotated by a drive (not shown as such) about an axis extending generally longitudinally of- elongated support members 28,30.

During the test operation brake 12 can be actuated by means of a supply of hydraulic fluid to its actuating cylinder (not shown) in the usual manner as if it were mounted in a vehicle. This causes the usual (relatively small) degree of axial sliding movement of the brake discs.

As thus far described, apparatus 10 corresponds to dynamometer apparatus not differing significantly (for the purposes of the present invention) from conventional such apparatus. However, for the purposes of the present embodiment of the present invention, there is additionally provided as part of apparatus 10, a treatment chamber 32 enclosing brake 12 and apparatus module 20 and part of elongated support members 28 and 30, as shown in the drawing. Treatment chamber 32 forms a housing entirely enclosing these latter-mentioned portions of apparatus 10 and also provides the following additional and important structures and functions.

Firstly, there is provided in the base of chamber 32 a bath or reservoir 34 to contain a supply of a treatment medium 36 which is to be applied to brake 12, as described below.

Thus, reservoir 34 serves to contain the body of treatment medium 26 and is provided with dosage means in the form of air jet means (shown diagrammatically at 38 in the drawing) which serves the dual function of agitating the treatment medium so as to ensure that such is generally reasonably uniformly mixed in terms of its constituents (to be discussed below) and so that doses of it can be applied by being projected in droplets towards disc brake 12.

Treatment medium 36 comprises a liquid medium (usually water or water-based) forming the entire or substantially the entire liquid content of the treatment medium, together with an abrasion or corrosion-promoting agent, or both. In this embodiment, the liquid medium is water and the abrasion-promoting agent comprises sand and/or soil particles (which in practice may be conveniently described as mud).

Air jet means 38 is adapted to operate at two levels of input power. At the first lower level of input power the air jet produces an agitating effect (at the five locations 38,42 shown) in relation to the treatment medium 36 in reservoir 34. At the second level of power, the air jet means effectively blasts (at location 38) the treatment medium 36 containing the generally uniformly distributed abrasive particles and acid medium towards brake 12, as shown at 40 which indicates the droplets of the treatment medium proceeding towards the brake.

It will also be noted in the drawing that air jet means 38 which is located directly below brake 12 and does itself effect both agitation of the treatment medium and droplet projection, is additionally provided with four uni

functional air jet units 42 at intervals along the length of reservoir 34 which operate at the lower power level to cause agitation of the treatment medium 36 and thus uniform dispersal of the mud in the bath.

In this embodiment, the air jet means 38 and 42 may be varied in construction significantly while meeting the requirements of the invention. Total uniformity of dispersion of the soil or sand or other particles is not essential, provided sufficient of such particles reach the relatively movable surfaces for abrasion-production purposes, and the extent of agitation can be adjusted accordingly. Likewise, alternative methods of agitation such as rotary mechanical agitation may be adopted, and such a system could be used for projecting droplets of the treatment medium towards the brake structure in place of the air jet system.

With regard to the treatment medium itself, as noted above, this will usually be based upon water and may be water alone, since water is versatile in this regard for providing a dispersion medium at an economical cost, and which promotes the electrochemical reactions which are the basis for the initiation of corrosion. However, for particular circumstances, an alternative liquid medium may be adopted. The acceleration of the corrosion process is most effectively achieved by use of an acid additive to the main body of the liquid treatment medium. Where a strong acid such as dilute hydrochloric acid or dilute sulphuric acid is employed, then very modest amounts of the already dilute acid will be sufficient to produce a substantial acceleration of the corrosion process. Where less-highly ionised acids are employed, then correspondingly, larger dosage will be required.

As an example of an acidified and highly ionic mud bath embodiment employed for test purposes, the following

content has been tested : a) 0. 75 kg per litre top soil (sieved) b) 25g per litre common salt (sodium chloride) c) 0.05g per litre sulphuric acid d) 0.05g per litre sulphur dioxide e) 1 litre water and in this acidified and abrasive treatment medium, the top soil and water produce a neutral mud to which the sodium chloride adds a neutral but highly ionic (and therefore electrochemical action-inducing) content. To this, the sulphuric acid and sulphur dioxide add significant acidification whereby the pH is significantly lowered.

Regarding the treatment chamber 32, this is in the form of a containment housing to enable the droplet application process to proceed with will-defined containment of the airborne droplets within the test facility in which the dynamometer apparatus is located.

Typically, the housing comprises a generally rectangular sheet metal fabrication having the reservoir structure constructed in its base portion. The latter may be simply in the form of a liquid-tight base region of the chamber in which the liquid treatment medium may collect, and which is provided with the above-discussed air jet means, or alternative structures.

Chamber 32 is provided with access means in the form of a releasable hatch or other closable entry facility enabling the brake to be initially mounted therein. The access means (not shown) provides means also for inspection of test progress from time to time, as the test work proceeds. In addition, window means may be provided for observation of the proceeding work, but in such a case,

there is probably the need for internal"windscreen washing and wiping"facilities in view of the mud spraying

procedures carried out within the chamber.

It is of particular significance in relation to the embodiments of the invention that the installation (and subsequent removal after testing) of the brake apparatus to be tested, together with the ongoing test work, can be carried out in a straightforward manner and without the need for any attention to the drive or actuation facilities (other than on initial installation and final removal), so that the inconvenience and inefficiency of previous attempts to provide means for immersion treatment with water are avoided.

In the embodiment, the location of the air jet 38 (or other) means which produces the droplets and directs them towards the brake is shown as being below the location of the brake structure under test. Such a disposition is not ideal for direct application of the projected droplets to the slidable structures of a brake of the kind comprising axially shiftable discs and a fixed caliper, wherein the caliper at least is generally located above the axis of rotation of the discs. However, the brake attitude can for test purposes be inverted if so desired (though the friction element mountings will not have been designed for such use), or the droplet projection facility may be redesigned to enable droplet generation to occur at the desired location, for example above the brake, by use of a suitable pump and nozzle facility adapted to cope satisfactorily with abrasive-containing and corrosiveliquid materials.

Amongst other modifications which could be made in the above embodiment while remaining within the scope of the invention are substantial changes to the structure and arrangement of the brake test rig. Indeed, the broader aspects of the invention are applicable to other automotive running gear such as suspension components eg shock

absorbers/dampers which would require substantial differences from the test rig for a disc brake, in terms of power input for causing the article under test to carry out its normal functions. Equally, the chamber 32 may be modified significantly as discussed above, and likewise, its internal structures and operating systems.

Likewise, as an alternative to the air jet-based dosage means there may be provided alternative dosage means for example rotary brush means adapted to apply the treatment medium to the running gear at selected locations thereon an in varying amounts accordingly.

Claims (18)

1. A method of testing automotive running gear in the form of a disc brake, the method comprising: a) providing non-vehicular apparatus to mount and drive and/or actuate said running gear for testing the carrying-out of its designed functions otherwise than on an automotive vehicle; b) causing said mounting and drive and/or actuation apparatus to effect such testing by carrying out of the designed functions of said running gear for test purposes and; c) the step of applying to said running. gear at least once during a continuous period extending from before to after said testing, a treatment medium comprising at least a liquid medium capable of causing or assisting abrasion and/or corrosion of said running gear ; characterised by: d) said step of applying to said running gear at least once during said period, comprising causing droplets of said treatment medium to be projected towards said running gear from a supply of said medium, so as to cover one or more selected portions of said running gear and penetrate where possible and/or test for penetration between at least those relatively movable portions thereof which are caused to effect such relative movement by said driving and/or actuation thereof; and e) said step of applying to said running gear at least once during said continuous period, and said step of causing said mounting and drive and/or actuation apparatus to effect such testing, being carried out in a sequence of test steps including at least one step of driving and/or actuating said running gear after at least one step of

applying said treatment medium to said running gear without the need to dismount and remount said running gear between successive steps or to disconnect and reconnect a drive thereto; and f) repeating aid sequence of test steps for a period sufficient to cause said treatment medium to assist the production of wear of said running gear and/or test for penetration as aforesaid.

2. A method of testing automotive running gear comprising the step of applying to said running gear doses of a liquid treatment medium which are applied to said running gear from a supply of said medium so as to cover and penetrate where possible and/or test for penetration between movable portions thereof, said treatment medium comprising a liquid medium or a dispersion or emulsion or solution in a liquid medium of a treatment medium comprising at least one abrasion or corrosion promoting agent.

3. A method according to claim 1 or claim 2 characterised by the step of causing said supply of treatment medium to comprise water.

4. A method according to claim 1 or claim 3 characterised by the step of causing said supply of said treatment medium to comprise a dispersion or emulsion or solution in said liquid medium of said treatment medium of at least one abrasion or corrosion-promoting agent.

5. A method according to any one of claims 1 to 4 characterised by said step of causing said supply of treatment medium to comprise as aforesaid comprising agitating a supply of said liquid medium and a supply of

solid abrasive particles so as to disperse said particles therein.

6. A method according to claim 5 characterised by said step of agitating comprising causing air jet means to agitate a body of said liquid medium and said abrasive particles.

7. A method according to any preceding claim characterised by said step of applying said treatment medium to said running gear comprising causing air jet means to project said droplets of said treatment medium towards said running gear.

8. A method according to claim 2 characterised by said doses being applied by means of air-carried droplets.

9. A method according to claim 2 characterised by said doses being applied by rotary brush means.

10. Apparatus for testing automotive running gear in the form of a disc brake, the apparatus comprising: a) non-vehicular apparatus to mount and drive and/or actuate said running gear for testing the carryingout of its designed functions otherwise than on an automotive vehicle; b) said mounting and drive and/or actuation apparatus being adapted to effect such testing by carrying out of the designed functions of said running gear for test purposes; and c) said apparatus being adapted to permit a user to apply to said running gear at least once during a continuous period extending from before to after said testing, a treatment medium comprising at least a liquid

medium capable of causing or assisting abrasion and/or corrosion of said running gear ; characterised by: d) said apparatus comprising means to apply to said running gear at least once during said period, droplets of said treatment medium to be projected towards said running gear from a supply of said medium, so as to cover one or more selected portions of said running gear and penetrate where possible and/or test for penetration between at least those relatively movable portions thereof which are caused to effect such relative movement by said driving and/or actuation thereof; and e) said apparatus being adapted to carry out a sequence of test steps including at least one-step of driving and/or actuating said running gear after at least one step of applying said treatment medium to said running

gear without the need to dismount and remount said running . gear between successive steps or to disconnect and reconnect a drive thereto.

11. Apparatus for testing automotive running gear comprising means for applying to said running gear doses of a liquid treatment medium which are applied to said running gear from a supply of said medium so as to cover and penetrate where possible and/or test for penetration between movable portions thereof, said treatment medium comprising a liquid medium or a dispersion or emulsion or solution in a liquid medium of a treatment medium comprising at least one abrasion or corrosion promoting agent.

12. Apparatus according to claim 10 or claim 11 characterised by said supply of treatment medium comprising water.

13. Apparatus according to claim 10 characterised by said supply of said treatment medium comprising a dispersion or emulsion or solution in said liquid medium of said treatment medium of at least one abrasion or corrosion-promoting agent.

14. Apparatus according to any one of claims 10 to 13 characterised by said supply of treatment medium comprising an agitated supply of said liquid medium and of solid abrasive particles disperse therein.

15. Apparatus according to claim 14 characterised by air jet means adapted to agitate a body of said liquid medium and said abrasive particles.

16. Apparatus according to claim 14 or claim 15 characterised by air jet means to project said droplets of said treatment medium towards said running gear.

17. Apparatus according to claim 11 characterised by said doses being applied by means of air-carried droplets.

18. Apparatus according to claim 11 characterised by said doses being applied by rotary brush means.