ARRANGEMENT AND METHOD FOR ACTIVATING AN EMERGENCY BRAKE FUNCTION WITHIN A VEHICLE

Abstract: The invention relates to a device for activation of an emergency brake function (8; 8') within a vehicle (1) in dependence of whether a regular brake function, comprising a first brake circuit and a second brake circuit, is out of order. The invention is characterised by comprising a first sensor (20; 20') for detecting whether the pressure (p1) in the first brake circuit falls below a first limit value (P1G<), a second sensor (21; 21') for detecting whether the pressure (p>2<) in the second brake circuit falls below a second limit value (p>2G), and means (16; 24, 25, 26) for activation of said emergency brake function if the pressure (P1) in the first brake circuit falls below the first limit value (p1G) at the same time as the pressure (P2) in the second brake circuit falls below the second limit value (P2G). The invention also relates to a method for such activation of an emergency brake function. Through the invention, a secure activation of an emergency brake function is allowed, and a reduced risk of this emergency brake function being activated unnecessarily, i.e. when it is not needed.

Description: TITLE Arrangement and method for activating an emergency brake function within a vehicle. TECHNICAL FIELD The present invention relates to an arrangement for activating an emergency brake function for a vehicle in dependence of whether a regular brake function, comprising a first brake circuit and a second brake circuit, is out of order. The invention also relates to a method for such activation of an emergency brake function. BACKGROUND ART In connection with transportation of heavy loads, e.g. in contracting work, vehicles of the articulated dumper type are frequently used. Such vehicles may be operated with large and heavy loads in areas where there are no roads, for example during transports in connection with road and tunnel building, sand pits, mines and similar environments. An articulated dumper of an as such known kind is constructed with a forward vehicle section, a so-called engine unit, in turn comprising a forward frame, supporting a/o an engine and a front wheel axle. Further, the dumper comprises a rear vehicle section in the form of a so-called load-carrying unit having a rear frame in turn supporting two wheel axles, a forward bogie axis and a rear bogie axis. The vehicle is commonly designed for switching between operations using various driving wheel combinations, all six wheels on the three axes being selectively operable as driving wheels, depending on the prevailing operating conditions. An articulated dumper may have a weight in the order of 15-30 metric tons and may be loaded with a payload in the order of 20-35 tons. In an articulated dumper, the frame of the engine unit is connected to the frame of the load-carrying unit by means of a special articulation joint, allowing the engine unit and the load-carrying unit to pivot in relation to each other about an imaginary longitudinal axis, i.e. an axis extending in the longitudinal direction of the vehicle. This articulation joint also allows pivoting about a vertical axis for steering of the vehicle. In this manner, the engine unit and the load-carrying unit are allowed to move substantially independently of each other. This reduces the stress loads acting on the vehicle, especially when operating in difficult terrain. Normally, an articulated dumper is equipped with a diesel engine and an automatic transmission having for example six forward gear ratios and two reverse gear ratios. For braking of the vehicle, an operating brake system is used, preferably of the hydraulic type and divided into two brake circuits, a first brake circuit intended for the engine unit and a second brake circuit intended for the load-carrying unit. Said brake system commonly comprises conventional disc brakes arranged for braking of the respective wheel. Besides the operating brake system, further brake functions are also commonly utilised in an articulated dumper. As an example of such an additional brake function, a retarder integrated in the transmission could be mentioned, i.e. a hydraulic brake device that, in a known manner, acts on a turbine shaft of the transmission for braking the vehicle. During braking of the dumper, the driver uses a brake pedal designed in such a way that when depressed, it will initially cause a retarder activation, and if depressed further, cause the retarder and the operating brakes to work together. Thus, by primarily using the retarder, a reduced wear of the operating brake system and an increased operator braking comfort will be achieved. The retarder may also be activated by means of a separate retarder pedal that, when depressed, will only cause braking by means of the retarder. Another brake function commonly used in connection with an articulated dumper is an engine brake. This brake function, frequently used with diesel engines, is controlled by means of a separate control and comprises a throttle that, when actuated, will restrict the flow of exhaust gases from the engine during its exhaust phase. This will create a back pressure in the exhaust system, causing a braking effect. A further brake function utilised in an articulated dumper consists of a parking brake, as such commonly arranged for being activated in order to secure that a stationary and parked vehicle will not move. It is known in the art to arrange a parking brake so as to act, when actuated, upon a cardan shaft, extending rearwards from the engine to the load-carrying unit. More specifically, the parking brake comprises a brake caliper acting on a brake disc, said brake disc in turn being fitted on said cardan shaft. The parking brake can be activated by the driver, preferably through a lever or a control in connection with the driver's seat in the vehicle. It is known in the art to utilise a parking brake of the spring brake type, meaning that it's clamping action is caused by a spring force, and it is released by means of a compressed air circuit, by the aid of which the spring force can be overcome so as to release the brake. The parking brake gets it's compressed air supply from a compressor provided on the dumper, via a compressed air container and a parking brake valve, arranged in connection with the previously discussed control, that can be activated by the driver. Beside the general purpose of actuating the parking brake in connection with parking the dumper, there is a requirement for using the parking brake as an emergency brake, in case the normal operating brake system should cease to function. More specifically, there is then a requirement for automatic actuation of the parking brake, as the driver will not always make a correct determination of when the emergency brake has to be used. If the parking brake were to be actuated during driving, this would entail a sudden retardation of the vehicle. This in turn could cause personal injuries and equipment damage. For this reason it is desirable not to activate the parking brake inadvertently. However, a spurious fault, e.g. a broken cable or other simple faults in the vehicle electrical system - that should not normally lead to any actuation of an emergency brake function - could cause the parking brake to be actuated though not really necessary. As such situations should be avoided, there is a requirement for improved systems preventing the parking brake from being automatically activated when not needed. DISCLOSURE OF INVENTION Thus, a major object of the present invention is to provide an improved arrangement for activating the brake function of a vehicle, especially an articulated dumper, whereby the problems discussed above will be resolved. This object is achieved by means of an arrangement, the characterising features of which are defined in the appended claim 1. The object is also achieved by means of a method, the characterising features of which are defined in the appended claim 7. The invention consists of an arrangement for activation of an emergency brake function of a vehicle in dependence of whether a regular brake function, comprising a first brake circuit and a second brake circuit, is out of order. The invention is characterised by comprising a first sensor for detecting whether the pressure in the first brake circuit falls below a first limit value, a second sensor for detecting whether the pressure in the second brake circuit falls below a second limit value, and means for activation of said emergency brake function if the pressure in the first brake circuit falls below the first limit value at the same time as the pressure in the second brake circuit falls below the second limit value. Through the invention an advantage is achieved in that it allows for safe activation of an emergency brake function and a reduced risk of activating said emergency brake function unnecessarily, i.e. when not needed. Advantageous embodiments of the invention are described in the subsequent dependent claims. DESCRIPTION OF DRAWINGS The invention will be explained more fully in the following, with reference to a preferred embodiment example and the enclosed drawings, in which: Fig. 1 shows, in principle, an articulated dumper with which the invention can be utilised, Fig. 2 shows, in block diagram form, the functional principle of the invention, with reference to a first embodiment, Fig. 3 shows the function of the invention with reference to a second embodiment, and * Fig. 4 shows the function of the invention with reference to a third embodiment. PREFERRED EMBODIMENTS Fig. 1 shows a strongly simplified side elevational view of an articulated dumper 1 with which the present invention is intended to be used. However, the invention will not be limited for use with this kind of vehicle, but could in principle be used with all kinds of vehicles where there is a need for secure activation of an emergency brake function, especially for preventing the emergency brake function from being applied unnecessarily. Fig. 1 thus illustrates an articulated dumper 1 , a type of vehicle as such previously known. In the following, the vehicle will not be described in detail, but only the components and functions of the vehicle necessary for an understanding of the invention. In an as such known manner, the dumper 1 comprises an engine unit 2 with a front wheel axle 3. The dumper 1 also comprises a load-carrying unit 4 having two wheel axles, i.e. a forward bogie axle 5 and a rear bogie axle 6. The engine unit 2 and the load-carrying unit 4 are interconnected via a special articulation joint 7, in an as such known manner allowing the engine unit 2 and the load-carrying unit 4 to move substantially independently of each other. All wheel axles 3, 5, 6, can be braked by an operating brake system, preferably arranged in the form of two brake circuits (not shown in detail), more particularly a first brake circuit intended for the engine unit 2 and a second brake circuit intended for the load-carrying unit 4. In an as such known manner, the operating brake system comprises (not shown) disc brakes acting on the respective wheel of the dumper 1. Beside the above operating brake system, the dumper is preferably also equipped with further brake functions, not shown in Fig. 1 but comprising a retarder, in the known manner integrated in the transmission of the dumper 1 , arranged adjacent to the vehicle engine on the engine unit 4. A further brake function in the form of an engine brake is preferably also provided on the dumper 1. In a known manner, the engine brake comprises a throttle, controlled by a control member and utilised to prevent the outflow of exhaust gases from the engine during its exhaust phase. This will create a back pressure in the exhaust system, which can be used to brake the vehicle. The retarder as well as the engine brake can be activated by the driver by means of suitable controls. Furthermore, the retarder and the engine brake may, if necessary, be activated automatically by means of a dedicated control unit. The dumper 1 also includes a further brake function in the form of a parking brake. The comprised components thereof are not shown in detail in the drawings. In a manner as such previously known, the parking brake comprises a brake caliper acting on a brake disc, in turn attached to a cardan shaft extending from the engine of the dumper to the load-carrying unit 4 for driving the wheel axles 5, 6 of the load-carrying unit 4. The parking brake can be activated by the driver, preferably through a lever or a control in connection with a driver's seat in the engine unit 2. Fig. 2 illustrates in detail how the compressed air system of the dumper 1 is configured, and how the invention may be used for actuation and release of a parking brake 8 of the dumper. According to the embodiment, the parking brake 8 is a spring type brake, meaning that it is applied by means of the force from a powerful spring 9 and is released b means of compressed air delivered via a compressed air circuit 10. When releasing the parking brake 8, the spring force of the spring 9 is thus overcome by means of supplied compressed air. When this supplied compressed air is evacuated and the pressure drops to atmospheric pressure, the parking brake will be re-applied, the spring 9 thereby pushing a (not shown) push rod, causing a mechanical clamping of a (not shown) brake disc. The compressed air circuit 10 receives its compressed air supply from a compressor 11 provided in the dumper and being connected to a reservoir 12 via a compressed air regulator 13. There is also a regeneration tank 14 connected to the compressed air regulator 13. From the first reservoir 12, the compressed air circuit is connected to the parking brake 8 via a parking brake valve 15 and a special valve arrangement 16, to be described in detail below. From the reservoir 12 there is also a connection to other compressed air consumers in the dumper, here indicated symbolically by the reference number 17. Such further compressed air consumers may for example consist of a differential lock device, an engine brake, a horn or similar functions. Furthermore applies, that the parking brake valve 15 is preferably arranged in connection with a control means, e.g. a lever, available for operation by the vehicle driver. The valve arrangement 16 will now be described in detail. It is a basic principle behind the invention that the valve arrangement 16 comprises a first valve 18, adapted to assume a first position or a second position depending on a detected value relating to the pressure pi prevailing in the first brake circuit, i.e. the brake circuit arranged in the engine unit 2 (compare Fig. 1). Similarly, it is a basic principle behind the invention that the valve arrangement 16 comprises a second valve 19, adapted to assume a first position or a second position depending on a detected value relating to the pressure p 2 prevailing in the second brake circuit, i.e. the brake circuit arranged in the load-carrying unit 4. To this end, a respective valve 18, 19, is connected to a first pressure sensor 20 for detecting the pressure pi in the first brake circuit, and a second pressure sensor 21 for detecting the pressure p 2 in the second brake circuit, respectively. The valves 18, 19 are of an as such known type comprising a (not shown) solenoid that can be energised to set the valve to a first position, the valve being biased into a second position by means of a (not shown) spring when the solenoid is not energised. The first valve 18 and the second valve19 are connected, via a shuttle valve 22, to a third valve 23. It is a basic principle behind the invention that the three valves 18, 19, 23 and the shuttle valve 22 are interconnected in such a way that the third valve 23 assumes a first position when both the first valve 18 and the second valve 19 are set to a first position, indicating that the respective pressures pi, p 2 in each brake circuit fall below their predetermined limit values, pι G and p 2G , respectively. Further, the third valve 23 will assume a second position if either one of the first valve 18 or the second valve 19 are assuming a position indicating that their respective limit pressures p 1Gl P2 G , are exceeded. In other words; the third valve 23 will assume said first position if both of the two brake circuits have ceased to function, and will assume said second position if at least one of the two brake circuits is working properly. Fig. 2 illustrates the function of the invention, more specifically in a condition where the parking brake 8 is actuated, the compressed air normally (i.e. when the parking brake 8 is not actuated) holding the spring 9 back having been evacuated to the atmosphere via the third valve 23, which to this end is assuming its first position, in which the compressed air connection leading to the parking brake 8 is connected to the atmosphere via the third valve 23. This situation thus corresponds to an emergency situation in which both vehicle brake circuits have ceased to function, i.e. the brake pressure in both of the respective brake circuits fall below their respective limit values pι G , P 2 G- The third valve 23 has assumed its first position through compressed air having been fed via the parking brake valve 15 (see Fig. 2) up to the first valve 18 and to the second valve 19. In the current condition, the pressure sensors 20, 21 have detected that the brake pressure in each brake circuit falls below its respective limit value PI G , P2 G , causing the first and second valves 18, 19 to be in a state corresponding to no compressed air being conducted on to the third valve 23. As long as this condition prevails, no compressed air will be fed up to overcome the force of the spring 9. Thus, the parking brake 8 will remain actuated as long as this condition remains. This is based upon the initially stated requirement of actuating a parking brake in an emergency situation corresponding to the pressures within both brake circuits falling below a certain value. This applies because the dumper can normally be operated - at least for a short while - with only one brake circuit functioning, even if the other brake circuit is out of order. If, for example, the first pressure sensor 20 should indicate that the pressure pi in the first brake circuit is higher than its corresponding limit value pι G , this will entail that the first valve 18 will assume a position in which compressed air is fed from the parking brake valve 15 and up to the shuttle valve 22. From there, the compressed air is fed on to the third valve 23, which is then actuated to assume a position where a compressed air connection is created from the parking brake valve 15, via the third valve 23 and up to the parking brake 8. More specifically, compressed air will then be fed up to and overcome the force of the spring 9, thus releasing the parking brake. A corresponding sequence of events applies if the second pressure sensor 21 should indicate that the pressure P2 in the second brake circuit is higher than its corresponding limit value p2G. In this case, compressed air will be fed from the parking brake valve 15, via the second valve 19 and up to the shuttle valve 22. From there, the compressed air is fed on to the third valve 23, which entails that compressed air is fed via the parking brake valve 15, via the third valve 23 and up to the parking brake 8. In analogy with what has been explained above, this entails that the parking brake 8 is released. Consequently, it can be stated that a basic principle behind the invention is that the parking brake will only be automatically actuated as an emergency brake function if the brake pressures pi, p 2 in both brake circuits are excessively low, i.e. fall below their limit values pic and p 2 G, respectively. The invention thus entails that the risk of an unintentional automatic activation of the parking brake can be eliminated, as, for example, a fault that would affect only one of the first valve 18 or the second valve 19 would not affect the third valve 23, and thus neither the function of the parking brake 8. Independently of the state of the valve arrangement 16, the parking brake 8 can also be actuated via manual operation of the parking brake valve 15. When the operator switches the parking brake valve 15 to a position corresponding to the parking brake 8 being actuated, the compressed air acting on and holding back the spring 9 will be evacuated via the parking brake valve 15. In this way the parking brake 8 will be actuated. The invention will now be described with reference to a further embodiment, shown in the form of a block diagram in Fig. 3. Similarly to what has been explained above, this second embodiment comprises a first pressure sensor 20' and a second pressure sensor 21', arranged for detecting the respective pressures pi , p 2 in the two brake circuits of the vehicle in question. Each one of the two pressure sensors 20', 21' is connected to corresponding inputs on a first electronic control unit 24. The control unit 24 is preferably computer based and functioning to detect whether the sensed pressure level values pi, p 2 in the brake circuits fall below limit values pic, P2G, corresponding to those pressure levels at which a proper function of the brake circuits can be guaranteed. One output of the first control unit 24 is connected to a parking brake 8' and is functioning to activate same in case said pressures pi, p fall below their respective limit values pι G , P2G. In case the parking brake 8' consists of a spring brake of a similar type as the one described above, the control unit 24 could preferably be arranged for activating an electrically controllable valve (not shown) for evacuation of the compressed air counteracting a spring in the parking brake 8'. In this way, the parking brake 8' will be actuated. In a similar manner to that of the embodiment shown in connection with Fig. 2, the parking brake 8' of Fig. 3 will also be actuated in case the pressures pi, p 2 in both brake circuits of the vehicle in question have fallen below their respective limit values. Thus, it can be stated that the function of the control unit 24 in Fig. 3 in essence corresponds to the function of the valve arrangement 16 described above with reference to Fig. 2. In analogy with what has been explained above, this will lead to a secure function when activating the emergency brake function. Fig. 4 shows, in block diagram form, a further embodiment of the invention. Similarly with what has been explained above, this third embodiment comprises a first pressure sensor 20' and a second pressure sensor 21', arranged to detect the pressures pi, p 2 in the two brake circuits of the vehicle in question. Each one of the two pressure sensors 20', 21', is connected to inputs on a second electronic control unit 25 and a third electronic control unit 26, respectively. The two control units 25, 26 are preferably computer based, and are independently functioning to detect whether the sensed pressure level values p 1 ( p 2 in the brake circuits fall below limit values pι G , p2G, corresponding to those pressure levels at which a proper function of the brake circuits can be guaranteed. One output of the second control unit 25 is connected to a first input of the above-mentioned first control unit 24, whilst one output of the third control unit 26 is connected to a second input of said first control unit 24. The first control unit 24, in analogy with what has been described above with reference to Fig. 3, is functioning to detect signals from the second and third control units, 25 and 26 respectively, indicating whether said pressures pi, p2 fall below their respective limit values pic, P2G- If this is the case, the first control unit 24 will activate a parking brake 8'. In case the parking brake 8' consists of a spring brake of a type similar to that described above, the first control unit 24 is preferably arranged for activating a (not shown) electrically controllable valve for evacuation of the compressed air acting on and holding back a spring in the parking brake 8'. In this way the parking brake 8' will be actuated. In a similar manner to that of the embodiment shown in connection with Fig. 3, the parking brake 8' according to Fig. 4 will also be actuated in case the pressures pi, p 2 in both brake circuits of the vehicle in question have fallen below their respective limit values. In analogy with what has been explained above, this will lead to a secure function when activating the emergency brake function, as the three control units 24, 25, 26, function independently of each other, and as, for example, a fault signal from the second control unit 25 will not automatically entail an actuation of the parking brake 8', as the first control unit 24 will only activate the parking brake if both the second control unit 25 and the third control unit 26 are signalling an excessively low brake pressure. The invention will not be limited to the embodiments described above and depicted in the drawings, but may be varied within the scope of the appended claims. For example, the invention can be utilised with various types of vehicles having two brake circuits, where there is a requirement for a secure emergency brake function without any unintentional activation. For example, the invention could be utilised to avoid unintentional actuation of the wheel brakes of a lorry or a bus. The parking brake described above could also be combined with other brake functions and also, for example, with a differential lock.

Claims: CLAIMS 1. An arrangement for activation of an emergency brake function (8; 8') within a vehicle (1) in dependence of whether a regular brake function, comprising a first brake circuit and a second brake circuit, is out of order, characterised by comprising a first sensor (20; 20') for detecting whether the pressure (p^ in the first brake circuit falls below a first limit value (p 1G ), a second sensor (21; 21') for detecting whether the pressure (p 2 ) in the second brake circuit falls below a second limit value (p 2G ), and means (16; 24, 25, 26) for activation of said emergency brake function if the pressure (p in the first brake circuit falls below the first limit value (pι G ) at the same time as the pressure (p 2 ) in the second brake circuit falls below the second limit value (p G ). 2. The arrangement according to claim 1, characterised b y said brake function consisting of a parking brake (8; 8') associated with the vehicle (1), functioning as an emergency brake. 3. An arrangement according to claim 1 or claim 2, characterised by the first pressure sensor (21 ) being connected to a first valve (18), adapted to assume a first position when the pressure (p^ in the first brake circuit falls below the first limit value (pι G ) and the second pressure sensor (21) being connected to a second valve (19), adapted to assume a first position when the pressure (p 2 ) in the second brake circuit falls below the second limit value (p 2G ), said first and second valves (18, 19) being connected to a third valve (23) adapted to assume a position for actuating said emergency brake function (8) when the first valve (17) is in said first position and the second valve (18) is in said first position. 4. An arrangement according to any one of claims 1-3, characterised by comprising a further valve device (15) for manual actuation of said emergency brake function. 5. An arrangement according to claim 1 or claim 2, characterised by comprising a first electronic control unit (24) to which the first sensor (20') and the second sensor (21 ') are connected, said control unit (24) functioning to activate said emergency brake function (8') if the first sensor (20') and the second sensor (21') indicate that the pressure (pi) in the first brake circuit falls below the first limit value (pι G ) and the pressure (p 2 ) in the second brake circuit falls below the second limit value 6. The arrangement according to claim 5, characterised b y the first sensor (20') being connected to the first control unit (24) via a second electronic control unit (25), and the second sensor (21') being connected to the first control unit (24) via a third electronic control unit (26), said second control unit (25) and third control unit (26) each functioning to detect whether the pressure in its associated brake circuit falls below their respective limit values (pι G , p 2G ), and by the second control unit (25) and the third control unit (26) being connected to the first control unit (24) for activation of said emergency brake function (8') if the second control unit (25) and the third control unit (26) indicate that the pressure (pi) in the first brake circuit falls below the first limit value (pι G ) and the pressure (P 2 ) in the second brake circuit falls below the second limit value (p 2G ). 7. A method for activation of an emergency brake function (8; 8') within a vehicle (1) in dependence of whether a regular brake function, comprising a first brake circuit and a second brake circuit, is out of order, characterised by comprising: detection of whether the pressure ( i) in the first brake circuit falls below a first limit value (p 1G ), detection of whether the pressure (P 2 ) in the second brake circuit falls below a second limit value (P2 G ), and activation of said emergency brake function if the pressure (pi) in the first brake circuit falls below the first limit value (pι G ) at the same time as the pressure (p 2 ) in the second brake circuit falls below the second limit value

Inventors: ELIASSON GOERAN, ELIASSON, GOERAN
Applicants: ELIASSON GOERAN, VOLVO ARTICULATED HAULERS AB, ELIASSON, GOERAN
Application year: 2001
Main classification: B60T8
IPC codes: B60T7, B60T13, B60T17