FR2872767A1 - Master cylinder for use in pneumatic actuator of vehicle, has bulb to detect variations of magnetic field of magnet, where the bulb is situated opposite to magnet so that current passes or not across bulb, when braking device is at rest - Google Patents

Abstract

The cylinder has a bulb (210) with switch having flexible contact blade. The bulb is placed in a plastic case (212) fixed on the body of the cylinder using elastic bushings (214, 215) to detect variations of a magnetic field of a magnet associated to a secondary piston (202) for detecting braking of a vehicle. The bulb is situated opposite to the magnet so that current passes or not across the bulb, when a braking device is at rest. An independent claim is also included for a pneumatic actuator.

Description

MASTER CYLINDER COMPRISING MEANS FOR DETECTING THE

  The present invention relates to a master cylinder comprising means for detecting the displacement of a movable element. A device 100 (FIG. 1) for braking a vehicle is generally controlled by a driver by means of a brake pedal 102 intended to transmit the control force exerted on this pedal 102 as far as a braking system. shown, comprising for example a caliper equipped with a piston and brake pads for clamping a disc secured to a braked wheel. To amplify the force exerted by this driver in a force F transmitted to the braking system, it is known to use a servomotor 104 pneumatic brake assist.

  For this, this servomotor 104 comprises a housing 106, cooperating with a control rod 108, connected to the brake pedal 102, and with a thrust rod 110 connected to a master cylinder 112 integrated in the servomotor, so that when the control rod 108 is moved by means of an action f transmitted by the brake pedal 102, the servomotor 104 moves the rod 110 by means of a thrust F of intensity greater than the intensity of the control f.

  For this purpose, the housing 106 comprises a cover 114 and a cylinder 116 cooperating with this cover 114 in a sealed manner, the internal volume of the housing 106 then being divided into a first chamber 118, called a rear chamber, and a second chamber 120, said front chamber, by means of a rigid skirt 122 and a flexible membrane 124 ensuring the seal between these two chambers 118 and 120.

  In a first step, when the servomotor 104 is inactive, that is to say when no braking is requested by the driver of the vehicle, the pressure in the rear chambers 118 and before 120 is kept below atmospheric pressure by means of a pumping device, not shown.

  In a second step, when the driver of the vehicle presses the brake pedal 102, the control rod 108 moves by the action of the control f and activates a pneumatic mechanism 126 so that an air intake to atmospheric pressure is carried out in the rear chamber 118.

  The pressure in the rear chamber 118 being greater than the pressure in the front chamber 120, the membrane 122 and the skirt 124 are subjected to a thrust F of intensity equal to PxS where P is the pressure difference between the two chambers and S the surface of the membrane.

  The displacement of the skirt 122 and associated rod 110 thus transmits a thrust F to the master cylinder 112 associated with the braking system.

  Moreover, the detection of braking is an essential operation in a vehicle, for example to generate a signal intended to light brake lights at the rear of the vehicle, thus indicating to other vehicles the beginning of braking, or to activate various braking electronic systems, such as an anti-lock system (ABS).

  Such detection currently uses a sensor 128 for moving the brake pedal 102 which comprises a first fixed connector 130a and a second connector 130b movable on the pedal so that the latter comes into contact with the first, closing an electrical circuit, when the driver presses the brake pedal 102.

  The present invention results from the observation of various problems raised by the braking detection method according to the prior art.

  A first problem results from the fact that, during the manufacture of the vehicle, it is necessary to perform a specific mounting of the sensor 128, its connectors 130a and 130b and cables associated with these elements (not shown) below the pedal 102, which represents a cost in production time specific to the assembly of these various elements.

  In addition, these assemblies, and the subsequent adjustments of these elements, are particularly difficult and difficult for the persons in charge of this work given the position of the brake pedal, located in a restricted space and difficult to access at the bottom of the door. cabin of the vehicle.

  Another problem lies in the fact that the current sensor 128 is a mechanical contact sensor which therefore has significant wear and, therefore, a risk of failures increasing over time.

  The invention solves at least one of these problems. The main subject of the present invention is a master cylinder of a vehicle comprising, means for associating a magnetic field with a movable element of the master cylinder, placed in displacement by a push rod of a servomotor, and means for detecting a displacement of this magnetic field, characterized in that said means for detecting a displacement of this magnetic field comprises a flexible blade switch bulb for detecting the displacement of the magnetic field.

  Thanks to the invention which is based on the detection of the displacement of a magnetic field and which does not require mechanical contact, the life of the system, and therefore its reliability, are improved.

  In addition, the brake detection system of a vehicle is integrated with the master cylinder so that integration of this system into the vehicle no longer requires specific mounting and adjustments.

  This eliminates the mounting operation specific to this system which reduces the cost of this operation.

  It is possible to use a rod or a piston of the servomotor to detect, via an associated magnetic field, its displacement so that, by detecting the displacement of a piston of the servomotor, the braking of the vehicle is detected.

  In one embodiment, the movable member is a piston 10 for compressing the master cylinder.

  In one embodiment, a magnetic field has been associated with a movable element of the master cylinder by arranging a magnet for it.

  In one embodiment, the magnet has an annular shape so as to be arranged at a compression piston of the master cylinder, increasing the pressure of the brake fluid circuit.

  In one embodiment, the magnet is located in a housing of the movable element of the master cylinder.

  In one embodiment, the flexible blade switch bulb is located with respect to the magnet associated with the movable element so that, when the braking device is at rest, no current flows through the switch bulb. with a flexible blade. Thus, the power consumption is reduced.

  According to one embodiment, the flexible blade switch bulb is located with respect to the magnet associated with the movable element so that, when the braking device is at rest, the blade switch bulb flexible is traversed by a non-zero current. Such an embodiment provides increased security since a device failure is easily detectable.

  Other features and advantages of the invention will become apparent with the description given below, by way of illustration and not limitation, with reference to the attached figures in which: FIG. 1, already described above, is a diagram FIG. 2 is an axial section of a master cylinder according to one embodiment of the invention; FIG. 3 shows a housing containing a flexible blade switch bulb used in a Embodiment of the invention FIG. 4 is a schematic diagram of the operation of a master cylinder in a type of embodiment normally referred to as closed. FIG. 5 is a diagram of the operation of a master cylinder in a type of embodiment referred to as FIG. normally open, - Figure 6 is a diagram of a master cylinder according to another embodiment of the invention.

  A first embodiment of the invention is described below with reference to FIG. 2 which is a diagrammatic section of a master cylinder 250 controlled by a rod (not shown) of thrust equivalent to the rod 110 of FIG. 1 and which couples with the primary piston 200.

  Thus, the primary piston 200 is connected, via thrust transmission means (not shown) of the servomotor, to a brake pedal as previously described so as to control a braking system.

  To perform this control, the primary piston 200 is secured to a first end 20la of a spring 201 whose second end 201b is integral with a secondary piston 202 also movable.

  More precisely, the secondary piston 202 is held by the second end 201b of the spring 201 and by a second spring 203 whose stiffness constant is lower than the stiffness constant of the spring 201.

  Thus, when the primary piston 200 moves to compress the spring 201, this action is transmitted to the secondary piston 202 which compresses the spring 203 so as to allow the displacement of the piston 202 and the compression of the brake fluid 205 controlling the pressure. activation of a braking system not shown.

  In this embodiment of the invention, a magnetic field is associated with the secondary piston 202, a moving element, by virtue of a ring magnet 204 integral with the piston 202.

  However, this secondary piston 202 reproduces the movement of the primary piston 200 until the total compression of the spring 203 so that, by detecting the movement of the piston 202 via the variation of the magnetic field associated with the magnet 204, the control is detected. braking of the vehicle.

  It should be noted that in this embodiment, the magnet 204 can be simply associated with the piston 202 thanks to its annular shape which allows easy and fast assembly of this magnet.

  On the other hand, the magnetization of the magnet 204 is such that its magnetic field is coaxial with respect to the axis of the piston 202.

  However, many other variants relating to the arrangement of the magnet vis-à-vis the piston are possible.

  Thus, in another embodiment, a magnet 208 is provided to the piston 202 by means of a tapping.

  Moreover, to detect the variations of the magnetic field of the magnet associated with the piston 202, a bulb 210 with a flexible blade switch, called I.L.S. subsequently, is placed in a plastic housing 212 fixed by means of elastic washers 214 and 215 on the body of the master cylinder.

  These spring washers 214 and 215 make it possible to fix the position of the housing 212 with precision and to make adjustments to optimize the operation of the detector.

  Figure 3 shows the various elements included in this housing 212. Thus, the I.L.S. 300 is mounted on a conductive metal structure 302 which is itself connected to a standardized connector (not shown), for example according to the manufacturer of the car in question, through an opening 304.

  This conductive structure 302 is placed in a plastic case 306, provided with an electromagnetic shield 308 around the I.L.S. bulb. 300.

  The plastic case has long notches 310 on the sides to be able to accurately adjust the assembly 320 containing the I.L.S. 300 relative to the piston magnet during assembly of the booster, this positioning of the housing 212 containing the I.L.S. 300 being a fine adjustment as described later with the help of Figures 4, 5 and 6.

  FIGS. 4 and 5 show two different examples of operation of I.L.S. bulbs, associated with the master cylinders 406 or 506, as a function of the signal emitted by this bulb when no braking is controlled.

  Thus, in Figure 4 is shown an embodiment where an I.L.S. bulb. 410 is passing, or closed, when the brake is not activated, this embodiment being referred to subsequently normally closed.

  Indeed, as shown schematically by the graph 430 which represents the intensity (ordinate 431) of the current flowing through the I.L.S. 410 as a function of the position (in abscissa 432) of the magnet 404 associated with the piston 407 considered, the intensity passing through the I.L.S. 410 is non-zero when the magnet 404 is at its rest position (zero abscissa).

  Subsequently, the I.L.S. 410 is closed or open depending on the position of the magnet 404, and thus the achievement of braking.

  For example, if the magnet 404 is inside a detection zone delimited by a continuous line 400, then the I.L.S. It is considered that the piston 407 is not moved and that, therefore, there is no braking command.

  On the other hand, if the magnet 404 is in a non-detection zone, outside a zone delimited by a dashed curve 402, then the I.L.S. 410 is open and no current flows through it (zero intensity).

  In this case, it is considered that the piston 407 is moved and braking is controlled.

  In this embodiment, the magnet 404 is arranged at the secondary piston 407 of the master cylinder 406 so that, at rest, it is located inside the zone defined by the continuous line 400, which means that the contact of the ILS bulb 410 is closed.

  When the driver brakes, the piston 407 moves the magnet 404 which enters the zone of non-detection, limited by the dashed line 402, which triggers the opening of the circuit associated with the I.L.S. 410 and thus signals braking.

  When the driver releases the brake pedal, the magnet returns to the detection zone, delimited by the continuous line 400, which closes the I.L.S. bulb.

  On the other hand, when the magnet 404 is between the two zones delimited, respectively, by the lines 400 and 402, the I.L.S. 410 retains, respectively, its on state or open depending on whether the magnet 404 comes from the detection zone, inside the curve 400, or that the magnet 404 comes from the non-detection zone, outside the dashed line 402 this phenomenon being due to magnetic hysteresis.

  This hysteresis phenomenon is represented on a projection 420 whose abscissa 421 represents the position of the magnet 404 along the axis 401 of the master cylinder 406.

  On the other hand, the ordinate 422 represents the intensity of the current flowing through the I.L.S. 410 which is equal to a value I, if the blades of the I.L.S. 410 are in contact, or none if the blades of the I.L.S. 410 are not in contact.

  Such a projection underlines the importance of a fine adjustment of the position of the I.L.S. 410 with respect to the master cylinder 406 and the magnet 404 to limit the hysteresis phenomenon and to allow the most sensitive detection possible of the displacement of the piston.

  FIG. 5 represents a second embodiment of a master cylinder 506 according to the invention in which the I.L.S. 510 is considered nonpassing, or open, when no braking is commanded.

  Such a situation is represented on the graph 530 which indicates the intensity (on the ordinate 531) of the current flowing through the I.L.S. bulb. 510 considered according to the position (in abscissa 532) of the magnet 504 associated with the piston 507.

  The abscissa zero corresponds to the rest position of the magnet, that is to say when the brake is not biased, the intensity of the current passing through the I.L.S. 510 being then zero.

  This intensity can become equal to I by moving the magnet 504 beyond a certain position X1 in a manner similar to the embodiment described above according to FIG. 4.

  Thus, the I.L.S. 510 is closed or opened depending on the position of the magnet 504 so that, if the magnet 504 is within a detection zone determined by the solid line 500, then the I.L.S. 510 is passing or closed and passes an intensity I. Conversely, if the magnet 504 is in a non-detection zone, outside the area defined by the dashed curve 502, then the I.L.S. 510 is open and no current flows through it (zero intensity).

  On the other hand, when the magnet 504 is between the two detection zones (curve 500) and non-detection zones (curve 502), as shown in FIG. 5, the I.L.S. 510 retains, respectively, its closed or open state depending on whether the magnet 504 comes from the detection zone, inside the curve 500, or that the magnet 504 comes from the non-detection zone, outside the dashed curve 502 This is due to the phenomenon of magnetic hysteresis.

  In other words, the magnet 504 integral with the piston 507 of the master cylinder 506 is in the zone of non-detection, delimited by the dashed curve 502, when the piston is at rest, that is to say in the absence of braking, which results in the circuit of the ILS bulb either non-passing or open.

  When the driver presses on the brake pedal and controls the braking device, the piston 507 of the master cylinder 506, and thus the magnet 504, move in such a way that the magnet enters the detection zone, defined by the continuous curve 500, which triggers the closing of the contact of the bulb ILS 510, and thus the establishment of a current I which passes through it.

  When the driver releases the brake pedal, the piston 504 of the master cylinder 506 returns to its initial position and the I.L.S. lamp circuit. 510 opens when the magnet 504 reaches the zone of non-detection, delimited by the dashed curve 502, the space existing between the line 500 and 502 being due to the magnetic hysteresis phenomenon.

  This operation is represented on the graph 520 which represents, on the abscissa 521, the position of the magnet 504 along the axis of the master cylinder 506 while the ordinate axis 522 represents the intensity of the current flowing through the bulb. THEY 510.

  In this embodiment, it is found that the maximum horizontal displacement 526 of the magnet must be less than a limit 528 which would cause the opening of the I.L.S. 510, this limit corresponding to the intersection of the axis of the master cylinder 506 and the discontinuous line 502.

  This positioning is measured horizontally by the horizontal distance Xo5 between the horizontal projection of a fixed side 508 of the master cylinder 506 on the axis of the master cylinder 506 and the horizontal projection 509 of the center of the I.L.S. bulb. 510 on the axis of the master cylinder 506.

  Vertically, this positioning corresponds to the vertical distance N5 between the axis 501 of the master cylinder 506 and the coast 503 in vertical projection of the I.L.S. bulb. 510.

  Another embodiment of the invention is shown in Figure 6 which shows a master cylinder 650 in axial section.

  In this embodiment, the annular magnet 600 is placed inside a primary piston 602, and not in the secondary piston 603 of the master cylinder as in the previous embodiments.

  In fact, the primary piston 602 starts moving as soon as the driver presses on the brake pedal to initiate the braking so that the detection of the movement of the primary piston 602 control can detect a start of braking.

  The interaction between the I.L.S. 604 considered and the magnet 600 must be adjusted as previously indicated with the aid of Figures 4 and 5 for the I.L.S. 604 opens or closes when the magnet 600 integral with the primary piston 602 moves.

  Moreover, in this embodiment, the housing 606 containing the I.L.S. 604 is placed in a housing so as to be parallel to the direction of movement of the piston.

  The present invention is capable of numerous variants such as, without limitation, the choice of the mobile element associated with a magnetic field, the place of a magnet when the latter is used to generate the magnetic field, the nature of the magnet , the nature of the magnetic field detector, the positioning of the ILS bulb when such a bulb is used as a detector, and its opening and closing characteristics of the blade contact and the choice to transmit braking to the rest of the vehicle systems specifying this information (such as stop lights) as a cutoff current flowing through the ILS bulb or on the contrary an activation of this current.

Claims (6)

  A master cylinder of a vehicle having means (204, 208, 404, 504, 600) for associating a magnetic field with a movable member (202, 407, 507, 602) of the master cylinder, moved by a push rod of a servomotor, and means (210, 300, 410, 510, 604) for detecting a displacement of this magnetic field, characterized in that said means for detecting a displacement of this magnetic field comprises a bulb with a flexible blade switch (210, 300, 410, 510, 604) for detecting the displacement of the magnetic field.   2. Booster according to claim 1 characterized in that the movable element is a piston (202, 407, 507, 602) compression of the master cylinder.   The master cylinder according to one of claims 1 or 2 characterized in that a magnet (204, 208, 404, 504, 600) is arranged in the movable element (202, 407, 507, 602) of the master. cylinder.   4. master cylinder according to claim 3 characterized in that the magnet (204, 404, 504, 600) has an annular shape so as to be arranged with a piston (202, 407, 507, 602) of compression of the master cylinder.   5. master cylinder according to claim 3 characterized in that the magnet (208) is located in a housing of the movable member (202).   Master cylinder according to claim 3, 4 or 5, characterized in that the flexible blade switch bulb (510) is located with respect to the magnet (504) associated with the moving element. (507) such that, when the braking device is at rest, no current flows through the reed switch bulb (510).   7. Servomotor according to claim 4 or 5 characterized in that the flexible blade switch bulb (410) is located vis-à-vis the magnet (404) associated with the movable member (407) of such so that when the braking device is at rest, the flexible blade switch bulb (410) is traversed by a non-zero current.