Patent Application
20060009901
More precisely, the invention relates to a motor vehicle braking device of the type comprising a parking brake.
It is known practice to fit motor vehicles with electronic driving aid devices to improve road holding or the effectiveness of the braking of the vehicles.
Amongst these electronic aid devices, mention can be made of ABS (Antilock Braking System), which is a device preventing the wheels from locking up during braking, or ESP (Electronic Stability Program) which is a device ensuring the stability of the vehicle particularly in turns or on a slippery pavement.
These electronic aid devices usually use a computer which processes data originating from sensors situated close to the wheels, and which automatically acts on the motor vehicle's braking device. The data are normally transferred between the sensors and the computer via electric cables.
The function of a vehicle parking brake is to immobilize the vehicle's wheels when the latter is parked. The parking brake may be actuated by mechanical or electric means whose correct operation it is desirable to monitor.
However, the addition of means of monitoring the parking brake requires a priori the management of monitoring data that must be transferred via electric cables as is the case with the aforementioned aid devices.
Now, the cost of installing electric cables in a vehicle increases with the number of these cables.
The main aim of the invention is to monitor the correct operation of a parking brake with the aid of simple and effective means, while minimizing the number of additional electric cables necessary for the operation of the means of monitoring the parking brake.
As a result, the subject of the invention is a motor vehicle braking device, of the type comprising a parking brake, characterized in that it comprises means for detecting the state of a member of the parking brake, these state detection means providing an item of information to a computer via an electric cable connecting this computer to a device placed close to the state detection means, called the adjacent device.
Thanks to this braking device, the motor vehicle comprises means detecting the state of a member of the parking brake, providing an item of information to the motor vehicle's computer. In addition, since the state detection means use an electric cable shared with the adjacent device, the number of additional cables necessary for the operation of the state detection means is limited.
A braking device according to the invention may also comprise one or more of the following features:
The invention will be better understood on reading the following description, given as an example only and made with reference to the appended drawings.
a to 7e are graphs representing over time signals transmitted in the form of pulses between the state detection means, according to a third embodiment, and the vehicle's computer.
A motor vehicle 10 schematized by four wheels 11 is represented in
Close to these state detection means 16, the braking device comprises a device 18 called the adjacent device. The adjacent device 18 interchanges data with a computer 20 of the braking device 12.
The interchanged data are carried by a signal, called the adjacent signal Sv, transmitted on at least one electric cable 22 connecting the computer 20 to the braking device 12.
The adjacent device is, for example, a wheel rotation detection device or a valve of the braking device 12, intended to control the inflow of brake fluid.
The computer 20 is for example the computer of an electronic aid device.
The state detection means 16 are connected to the electric cable 22, in order to be able to transmit to the computer 20 a signal, called the state detection signal Sp, carrying the data relating to the state of the parking brake member 14. Thus, the number of additional cables necessary to the operation of the state detection means 16 is limited because the electric cable 22 is common to the transmission of the adjacent signal and of the state detection signal. It may be considered that the adjacent signal Sv and the state detection signal Sp are multiplexed on the electric cable 22.
The braking device 12 comprises disk braking means equipping at least the front wheels of the vehicle.
Thus, with reference to
The state detection means 16 of the parking brake member 14 are supported by the caliper 28. These means 16 detect for example the movement or force sustained by the parking brake member 14. This member 14 may be a key intended to stop the stroke of the hydraulic cylinder in the position in which the wheel is immobilized.
The means 16 may detect two states of the parking brake member 14: a first state in which this member 14 is activated and a second state in which this member 14 is deactivated, which have been designated respectively by Ep1 and Ep2.
According to a first embodiment shown in
This wheel rotation detection device 32 comprises conventional means of the magnetic or optical type. In the example described, the detection device 32 comprises magnetic means such as a Hall effect probe H, supported by the hub carrier 24, associated with a phonic wheel 33 connected in rotation to the disk 23.
The wheel rotation detection device 32 can detect two states: a first state in which the wheel is immobile and a second state in which the wheel is rotating, which are designated respectively by Ev1 and Ev2.
The four states Ep1, Ep2, Ev1 and Ev2 detected by the means 16 (the first two) and the device 32 (the last two) correspond respectively to the four signals sp1, sp2, sv1 and sv2 intended to be transmitted on the electric cable 22.
The transmission to the computer 20, on a single electric cable 22, of the state data of the wheel rotation detection device 32 and of the state data of the state detection means 16 is carried out by means of a simple multiplexing consisting of summing the signals corresponding to the detected states. The various cases are assembled in the following table:
As will be specified in greater detail hereinafter, the values of the signals sp1, sp2, sv1 and sv2 must comply with certain relationships for the computer 20 to carry out an effective demultiplexing, that is to say for the computer 20 to differentiate between the summed signals.
The electric circuit comprises a first module 34 comprising the adjacent device 18, and various electric elements associated with the Hall effect probe H, particularly the current generators I1 and I2. On the electric cable 22, these generators provide:
The electric circuit in
The contactor 40 is open when the parking brake member is in the state Ep1, that is to say when it is deactivated, and is closed when the parking brake member is in the state Ep2, that is to say when it is activated.
The signal resulting from the multiplexing of the two signals is a current marked IT, transmitted on the electric cable 22. This current is equal to the sum of the currents created by the first two modules 34 and 38. The possible values of the current IT are assembled in the following table:
δIv designates the amplitude of the noise of the adjacent signal provided by the wheel rotation detection device 32. The four states are distinguishable from one another provided that the values of the current IT corresponding to these four states are different by twos to within 2δIv.
If in addition δIp designates the amplitude of the state detection signal noise, then the four states are distinguishable from one another provided that the current values IT corresponding to these four states are different by twos to within 2δIv+2δIp.
The electric circuit in
According to a second embodiment shown in
As in the first embodiment, the parking brake may have two states Ep1 and Ep2: a first state in which it is activated and a second state in which it is deactivated.
The items of information relating to the state of the parking brake member 14 and the items of information relating to the state of the valve 46 are multiplexed on the electric cable 22. The electric circuit corresponding to the second embodiment is identical to that of the first embodiment shown in
The first module 34 shown in
The possible values of the current IT are then assembled in the following table:
The remarks concerning the prescribed relations between the values of the currents I1, I2 and I3 are identical to those formulated in the description of the first embodiment.
According to a third embodiment not shown, the adjacent device 18 comprises a sensor capable of detecting more than two states. The adjacent device 18 may, for example, be a wheel rotation detection device, also providing an item of information relating to the direction of rotation of the wheel.
The data provided by the adjacent device 18 are carried by the adjacent signal Sv transmitted to the computer 20 on the electric cable 22. The
The signal Sp, carrying the data provided by the state detection means 16 of the parking brake member 14, is shown in
The signals Sp and Sv are multiplexed by summing them. The pulses are of different durations, so it is possible to distinguish them and demultiplex the signals.
The number of states that can be transmitted on the electric cable 22 increases as the transmission noise reduces.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04/07575 | Jul 2004 | FR | national |
