Source: http://www.sumobrain.com/patents/wipo/Vehicle-braking-systems/WO1990012717A1.html
Timestamp: 2019-11-12 21:25:11
Document Index: 645555608

Matched Legal Cases: ['art 52', 'art 53', 'arts 52', 'arts 52', 'art 53', 'art 53']

WIPO Patent Application WO/1990/012717
The invention relates to a vehicle braking system comprising a braking element (15) operable by a driver of the vehicle, control signal generating means responsive to the operation of the braking element, means braking at least one wheel of the vehicle in response to the control signals generated by the control signal generating means and reaction means responsive to the control signals to provide a force on the braking element (15) so as provide a variable artificial feel to the driver through the braking element.
PCT/GB1990/000640
GB2080458A
FR2463035A1
1. A vehicle braking system comprising a braking element operable by a driver of the vehicle; control signal generating means responsive to operation of the braking element; means braking at least one wheel of the vehicle in response to control signals generated by the control signal generating means; and reaction means responsive to the control signals to provide a force on the braking element to provide a variable artifical feel to the driver through the braking element.
2. A braking system as claimed in Claim 1, in which the control signals are proportional to a force applied to the braking element by the driver.
3. A braking system as claimed in Claim 2, comprising means for sensing the force applied to the braking element and providing input signals proportional thereto to the control signal generating means.
4. A braking system as claimed in claim 3, in which said sensing means comprises an electrical load cell.
5. A braking system as claimed in any preceding claim, comprising means for sensing the position and/or movement of the braking element and providing input signals to the control signal generating means proportional thereto.
6. A braking system as claimed in Claim 5, in which the position and/or movement sensing means comprises one or more linear variable displacement transducers.
7. A braking system as claimed in any preceding claim, in which the reaction means comprises a hydraulic actuator coupled to the braking element.
8. A braking system as claimed in Claim 7, in which the actuator is a double acting hydraulic actuator having a pair of opposed piston faces.
9. A braking system as claimed in Claim 8, in which the actuator is controlled by a servo valve responsive to the control signals to control the application of hydraulic fluid pressure to the opposed piston faces to operate the actuator.
10. A braking system as claimed in any preceding claim, in which the braking element is a brake pedal.
11. A braking system as claimed in any preceding claim, including error detection means operative to check whether the artificial feel is being provided to the braking element and to provide input signals to the control signal generating means in dependence thereon.
12. A braking system as claimed in Claim 11, in which on detection of an error by the error detection means outside a preset limit, the control signal generating means generates control signals to operate a safety system.
13. A braking system as claimed in any preceding claim, in which the control signal generating means is a computer.
14. A system as claimed in Claim 13, in which the computer is programmable to generate control signals dependent on requirements of the driver and/or the condition of the vehicle.
15. A vehicle braking system substantially as hereinbefore described with reference to the drawings.
16. A vehicle having a braking system as claimed in any one of Claims 1 to 15.
Hydraulic systems have many advantages, such as being self-lubricating (reducing the chance of seizure), having a low rate of wear and low friction, and enabling equal pressures to be exerted on all the brake shoes or calipers, even compensating for unequal wear or adjustment. Further, installation is generally easier than for mechanical systems because of the flexibility of the hoses.
According to the invention there is provided a vehicle braking system comprising a braking element operable by a driver of the vehicle; control signal generating means responsive to operation of the braking element; means braking at least one wheel of the vehicle in response to control signals generated by the control signal generating means; and reaction means responsive to the control signals to provide a force on the braking element to provide a variable artifical feel to the driver through the braking element.
Preferably the control signals are proportional to a force applied to the braking element by the driver.
In a preferred embodiment the system comprises means for sensing the force applied to the braking element and providing input signals proportional thereto to the control signal generating means, the sensing means preferably comprising an electrical load cell.
Preferably the system comprises means for sensing the position and/or movement of the braking element and providing input signals to the control signal generating means proportional thereto, said sensing means preferably comprising one or more linear variable displacement transducers.
Preferably the reaction means comprises a hydraulic actuator coupled to the braking element, the actuator preferably being a double acting hydraulic actuator having a pair of opposed piston faces.
The actuator is preferably controlled by a servo-valve responsive to the control signals to control the application of hydraulic fluid pressure to the opposed piston faces to operate the actuator.
The braking element can be a brake pedal.
Another preferred embodiment includes error detection means operative to check whether the artifical feel is being provided to the braking element and to provide input signals to the control signal generating means in dependence thereon. On detection or an error by the error detection means outside a pre-set limit, the control signal generating means preferably generates control signals to operate a safety system.
The control signal generating means is preferably a computer which can be programmable to generate control signals dependent on requirements of the driver or the condition of the vehicle.
The system 10 combines a primary active brake system and a secondary brake override system that provides the braking effort in the event of a system failure or when the active system is turned off. The Primary Active Braking System
which enters "a holder 23 of a linear variable differential transformer (LVDT) 24. The LVDT holder 23 is fixed adjacent to the cylinder 18 on a manifold block 75 housing the feel actuator 16. The LVDT 24 converts the mechanical displacement of the linkage element 20 (and therefore the displacement of the brake pedal 15) into an electrical signal which is transmitted to the microprocessor 25 to which the LVDT 24 is electrically connected. Other suitable devices may of course be used for converting the displacement into an electrical signal.
The feel actuator 16 is hydraulically connected to servo valve .28. Hydraulic transfer tubes 9 are provided in the manifold block 75 linking the hydraulic fluid lines from the servo valve 28 to each end of cylinder 18 so that the servo valve 28 may be used to control the movement of the piston 17 by hydraulic pressure to either side of the piston head 17a.
As will be seen in Figure 1 a non-return valve 29a is included in the hydraulic fluid line between the servo valve 28 and feel actuator. 16, for reasons described below. The non-return valve 29a is also connected to the pressure supply line 33 Via an isolating valve 31 described below. The non¬ return valve 29a opens on application of pressure thereto.
The servo valves .11, 12, 13, 14 are connected to the hydraulic pressure and return lines 33, 34 via connectors 32. One connector 32 connects a branch of the pressure and return lines to one pair of servo valves 11, 14 and the other connector 32 to the second pair of servo valves 12, 13. The Distribution Valve
As shown in Figure 1, one pair of ports 37, 38 feeds
.from one fluid line 58 from the master cylinder whilst the second pair of ports 39, 40 feeds from the second fluid line
59. A balancing valve 60 may be provided in one of the fluid 1
#~3 lines 58,^-59.
Within each chamber 46, 47, 48, 49 is a spool 51 comprising a concave first part 52 which is located in one end σi a concave second part 53, the two parts 52 and 53 being secured together by a screw 55. As shown the two parts 52 and 53 are αjξ. different materials in view of the possibly different fluids acting on the two parts. The spool 51 is slidable within the chamber 46, 47, 48, 49.
A compression spring 54 is also located in each chamber 46, 47, 48, 49, with one end located against an inside face 55 of the second spool part 53 so as to bias the spool 51 outwards to seal off the fluid passage 50 between the chamber 46, 47, 48, 49 and the associated servo valve 11, 12, 13, 14. The length of, the spool 51 is such that when it is biased as mentioned above brake fluid from the master cylinder 45 is free
When hydraulic pressure is applied via pressure line 33 to the end face 57 of the spool part 53 the bias of the spring 54 is overcome and the spool 51 moves to compress the spring 54 and seals off the chambers 46, 47, 48, 49 from the ports 37-40. Secondary Brakinσ System
A reaction to the driver's demand on the brake pedal 15 is provided by the feel actuator 16. To do ■ this the microprocessor 25 sends control signals to the servo valve 28 which is connected to the feel actuator 16 to apply pressure to either side of the piston head 17a. This is used to provide resistance to movement of the brake pedal 15 and to generally simulate the "feel" of braking. This "feel" may be altered by programming the microprocessor 25 to provide light or heavy braking or whatever the driver prefers.
Since the isolating valve 31 is energised the servo valves 11, 12, 13, 14 are connected to the pressure supply line via the connectors 32. The fluid pressure is controlled by each servo valve 11, 12, 13, 14 to operate each brake mechanism independently. The fluid pressure transmitted from the servo valves 11, 12, 13, 14 via fluid passages 50 is sufficient to overcome the preload on the springs 54 causing the spools 51 to move in the chambers 46, 47, 48, 49 to seal them off from the ports 37-40 from the master cylinder 45. The fluid remaining in the chambers 46_-49 is forced out of the chambers 46-49 via the ports 41-44 by movement of the spools 51 to the individual brake mechanisms to operate the brakes independently of each other. Secondary Braking
Various safety control loops may be incorporated in the overall braking system which are monitored by the microprocessor 25. An example described earlier in the provision of the LVDT 24 which checks whether the feel actuator 16 is in fact operating according to the control signals sent to the servo valve 28 by the microprocessor 25. The LVDT, load cell 21 and other sensors in the system are preferably duplex sensors. Their signals are duplicated and the signals combined to give a demand and an -error detection signal. Failures in the control loops can be detected by comparing the actual output from the system with a real time model of the system running in parallel. Any detected failures will result in de-energisation of the isolating valve 31.
Thus pressure applied to the pedal 15 will be transmitted by movement of the piston 17 with piston head 17a forcing the fluid out of cylinder 18, via the switching valve 70, into the cylinder 68 of the secondary actuator 68 to act on the piston head 66 of the secondary actuator 68. Thus, braking in this mode feels and performs similar to a standard unmodified hydraulic braking system.
Referring to the distribution valve 35, in secondary braking the .-ervo valves 11-14 are connected to the fluid return line 34 and the pressure applied to the spools 51 drops. The fo*ce of springs 54 is sufficient to overcome any residual pressure and force the spools 51 outwards towards the servo valves 11-14 to seal off fluid passages 50 from the chambers 46-49 and the ports 37-40 which communicate with the master cylinder 45 are uncovered.
Although the system described above operates primarily in dependence upon the load applied to the brake pedal, with appropriate modifications to the system it may be made
"responsi-ve to the position or movement of the brake pedal or any other parameter measurable in the system.
Next Patent: VEHICLE BRAKING SYSTEMS