WO2002087946A2

WO2002087946A2 - Servomotor comprising a jamming key

Info

Publication number: WO2002087946A2
Application number: PCT/FR2002/001391
Authority: WO
Inventors: Jean-Pierre Gautier; Philippe Richard; Pierre Pressaco
Original assignee: Robert Bosch Gmbh
Priority date: 2001-04-26
Filing date: 2002-04-23
Publication date: 2002-11-07
Also published as: FR2824034B1; WO2002087946A3; FR2824034A1

Abstract

The invention concerns a pneumatic servomotor for a motor vehicle comprising a mobile piston (22) driven by a plunger actuated by a control rod (38). The invention is characterised in that it comprises a substantially annular jamming key (60), which encloses a sleeve (58) passing through the piston and enclosing the plunger, which is mounted axially relative to the piston with a specific clearance (J), and which is capable, when an input force is applied on the rod (38), of being driven by the piston (22) to leave its support on the servomotor housing and tilt over the periphery of the sleeve (58), so that when the rod (38) and the plunger (46) return rapidly, the jamming key (60) transmits the reaction of the braking master cylinder to the piston (22) after the specific clearance (J) is absorbed.

Description

"Servomotor with a jamming key"

The invention relates to a pneumatic brake booster for a motor vehicle.

The invention relates more particularly to a matic tire booster for braking assistance for a motor vehicle, of the type which comprises a rigid envelope inside which is movable a transverse partition sealingly delimiting a front chamber, subjected to a first engine vacuum pressure, and a rear chamber subjected to a second pressure varying between the engine vacuum and the atmospheric pressure, of the type which includes a movable piston for actuating a master brake cylinder of the vehicle, secured to the partition mobile, and of the type which comprises a control rod which is capable of moving in the piston, selectively between a rest position and an extreme actuation position as a function of an axial input force exerted towards the front against a return force exerted on the rod by a return spring, of the type which comprises a plunger which is arranged at the front of the co mmande in the piston, of the type which comprises a three-way valve which comprises at least one annular rear seat of the plunger r and which i is likely to vary the second pressure prevailing in the rear chamber, in particular by connecting the front chamber and the rear chamber when the control rod is in the rest position or by gradually bringing the rear chamber into communication with atmospheric pressure when the control rod is actuated to cause the displacement of the piston, of the type in which, in the extreme position actuation of the control rod, a feeler forming the front end of a sleeve mounted to slide at the front end of the plunger is urged by the plunger in contact with a reaction disc secured to the rear face of the movable piston to transmit the reaction force which is transmitted from the master cylinder to the plunger and the control rod of the vehicle with the movable piston, and of the type in which, when the control rod is actuated or released at a determined speed which is greater than that of the balancing of the second pressure in the rear chamber of the actuator, the rod control and the plunger moves faster than the piston.

In known manner, such a conventional design has considerable drawbacks in terms of safety during an emergency braking situation. Indeed, a conventional servomotor has neither an independent feeler, nor a unidirectional clutch device for the feeler. A n end section of the plunger, forming a feeler, is capable of coming directly to stress the reaction disc secured to the rear face of the movable piston. In an extreme braking situation for which a maximum braking force is exerted on the control rod, the actuation of the control rod causes the actuation of the plunger also forming a feeler, which causes the maximum opening of the valve at three tracks so that the rear chamber is brought to atmospheric pressure. I t follows a displacement towards the front of the movable partition and the end of the plunger comes into contact with the reaction plate secured to the rear face of the movable piston.

Thus, the force exerted on the movable piston when the control rod is at the end of travel results from the assistance force which is caused by the difference in pressure on each side of the mobile wall and from the force exerted by the plunger r forming a feeler on said movable piston. The driver of the vehicle also feels the braking reaction force, which is transmitted from the movable piston to the plunger via the reaction disc.

However, it has been found that a good number of drivers, faced with an emergency braking situation, underestimated the risks involved, and that, after braking suddenly, they released their braking effort while maintaining a braking effort was essential to avoid an accident.

In fact, in the case of an extreme braking situation accompanied by a rapid displacement of the control rod, the plunger can come into contact with the reaction plate and transmit to the driver a feeling of maximum braking even before the difference pressure is maximum between the front and rear pressure chambers, which can lead the driver to relax his effort, even if he should be maintained r benefit from the maximum braking effort.

It is known from the prior art a booster r of the type described above which overcomes this drawback by blocking, when the plunger returns, a probe independent of the plunger r in contact with the reaction disc and therefore maintain maximum effort on the rear face of the movable piston even if the driver has partially relaxed his effort.

However, a servomotor of this type has the drawback, unlike a servomotor devoid of a one-way clutch, of requiring during its manufacture, the production of a socket, intermediate between the feeler and the plunger, in order to lock the probe in a precise axial position when the plunger returns.

This additional part considerably increases the cost of manufacturing such a booster.

The invention makes it possible to remedy this drawback by using an unidirectional clutch device which is illé latch on a dou ille comprising an integrated feeler as soon as the plunger is actuated, and which only participates in the blocking of the feeler when the diver returns.

To this end, the invention provides a servomotor of the type described above, characterized in that it comprises a unidirectional clutch device which comprises a substantially annular wedging key, which surrounds the socket, which is elastically recalled in support i on the casing of the booster, which is mounted axially with respect to the control piston with a determined play, and which is likely, when the input force is applied, to be driven by the piston control to quit its support on the casing of the actuator and switch around a generally transverse axis in order to get stuck on the periphery of the sleeve, in particular so that during a rapid return of the control rod and the plunger to a speed greater than or equal to the determined speed, the jamming key transmits the reaction from the brake master cylinder to the piston as soon as the determined clearance is absorbed.

According to other characteristics of the invention:

the feeler forming the front end of the sleeve consists of a cylindrical front section of the sleeve which is slidably mounted in a complementary front bore of the piston,

- The sleeve has a cylindrical rear section which is of a diameter greater than its front end section forming a probe, which is slidably mounted in a rear bore complementary to the piston, and which is resiliently biased towards the rear against the plunger by by means of a spring bearing on the piston,

the plunger is slidably mounted in a hole in the socket, a bottom front face of which allows the axial support of the plunger in the extreme actuation position of the control rod,

the wedging key is mounted in a recess which passes vertically through the piston, and it has the form of a substantially radial orientation plate which i is traversed by the sleeve, a lower end of the wedging key projecting out of the bushing opposite a support element of the envelope, the wedging key being also resiliently returned to meet a rear wall of the recess, - the rear section of the socket has a pair of diametrically opposite oblong slots of axial orientation and the plunger has a transverse hole, coinciding with the oblong slots, which are crossed by a transverse pin which projects transversely from both sides dou ille in particular to cooperate with the wedging key in order to return it to the rest position in support i on the support element of the casing of the booster,

- a first spring is interposed between the front face of the recess and the lower end of the wedging key,

- the pin is arranged in front of the wedging key,

- the first spring is tilted back and forth away from the axis of the booster,

- a second spring is interposed between the rear face of the recess and the upper end of the wedging key,

the upper end of the wedging key comprises a centering pin for the second spring,

the determined clearance is arranged between a contact face of the upper end of the wedging key and a front contact face of the recess of the piston,

- the determined clearance is arranged between a contact face of the upper end of the wedging key and the end of a fixed axial finger which crosses the piston and protrudes from a front face of the recess of the piston , - the upper end of the wedging key is slidably mounted with a radial clearance on a fixed axial finger which i passes through the piston and protrudes from a front face of the recess of the piston, and a leaf spring is arranged between the axial finger and the upper end of the wedging key, - the determined clearance corresponds to the sliding stroke of the upper end of the wedging key on the finger,

- the first spring is of axial orientation,

- the actuator has an additional release key which is mounted behind the jamming key in the recess, which has the shape of a substantially radial orientation plate which is traversed by the sleeve, the lower end of which protrudes from the sleeve and is interposed between the lower end of the wedging key and the support element of the envelope, and one upper end of which is coupled by means of an elastic coupling device to the upper end of the wedging key,

- The elastic coupling device comprises a jumper which encloses the upper end of the wedging key and of which a lug extending towards the rear crosses the upper end of the trigger key and carries a spring interposed between the jumper and the upper end of the trigger key,

- the determined clearance is arranged between the rear end of the jumper and the upper end of the trigger key,

- the pin is arranged between the jamming key and the triggering key, to recall the jamming key by means of the triggering key,

- The piston is made in two parts and has a body inside which is slidably mounted and recalled towards the rear a cylindrical cartridge which slidably receives the sleeve, the body and the cartridge being each perforated to form the receiving recess the wedging key, a lower end of which protrudes from the body opposite a support element i of the casing, a first spring being interposed in the cartridge between the front face of the recess and the upper end of the jamming key, and an additional plate-shaped triggering key, mounted in a jumper on the cartridge being supported on the rear of the upper end of the jamming key and being resiliently biased towards the front to the piston body by means of a second spring,

- the determined clearance corresponds to the stroke of the cartridge in the piston body. Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a view in axial section of a conventional booster,

FIGS. 2a to 2e are detailed views in axial section of a first embodiment of a booster according to the invention, shown successively in the rest position, slow application, slow application return, rapid application and rapid application return from the diver,

FIG. 3 is a perspective view of the elements of the booster in FIGS. 2a to 2e,

FIGS. 4a to 4e are detailed views in axial section of a second embodiment of a booster according to the invention, shown successively in the rest position, slow application, return of slow application, rapid application and rapid application return from the diver,

FIG. 5 is a perspective view of the elements of the booster of FIGS. 4a to 4e,

FIGS. 6a to 6e are detailed views in axial section of a third embodiment of a booster according to the invention, shown successively in the rest position, slow application, slow application return, rapid application and resumption of rapid application of the plunger,

FIG. 7 is a perspective view of the elements of the servomotor of FIGS. 6a to 6e,

FIGS 8a to 8e are detailed views in axial section of a fourth embodiment of a servomotor according to the invention, shown successively in the rest position, slow application, slow application return, rapid application and rapid application return of the diver,

FIG. 9 is a perspective view of the elements of the booster in FIGS. 8a to 8e, - Figures 10a to 10e are detailed views in axial section of a fifth embodiment of a booster according to the invention, shown successively in the rest position, slow application, slow application return, rapid application and rapid application return from the diver, and

- The fig 1 re 1 is a perspective view of the elements of the booster in FIGS. 10a to 10e.

In the following description, identical reference numerals designate identical parts or having similar functions.

By convention, the terms "front", "rear", upper "," lower "respectively designate elements or positions oriented respectively to the left, the right, the top or the bottom of the figures. figure 1 the set of a servo

10 conventional brake assist tire for a motor vehicle.

In known manner, the pneumatic actuator 10 comprises a rigid casing 12 inside which is movably mounted a transverse partition 14 which i sealingly delimits a front chamber 16, subjected to a first pressure "Pi" whose value is equal to the vacuum value of the vehicle engine, and a rear chamber 18 subjected to a second pressure "P ₂ ". The second pressure "P ₂ " is likely, as will be described later, to vary between the value of engine depression "Pi" and the value of atmospheric pressure ιι p II ^r a •

The front chamber 16 is supplied with pressure “Pi” via a vacuum conduit 20 which is connected to a source of vacuum in the vehicle, for example a vacuum prevailing in an intake manifold (not shown ) of a motor of the vehicle.

The pneumatic actuator 10 comprises a movable piston 22 of axis A which is integral with the movable partition 14. Inside of the casing 12, the movable partition 14 is returned elastically towards the rear by a return spring 24 which bears on the casing 12 and on a front face 26 of the movable piston 22. The front face 26 of the movable piston 22 carries a reaction cup 30 inside which is arranged, as will be seen below, a reaction disc 32 of elastomeric material. A front face 34 of the reaction cup 30 is integral with an actuating rod 28, which consequently is integral with the displacements of the movable piston 22, and which allows the actuation of a hydraulic master cylinder 36 for braking of the vehicle.

A control rod 38, which i for example is connected to a brake pedal of the vehicle via a coupling sleeve 41 which is arranged at its rear free end, is capable of moving in the movable piston 22, selectively as a function of an axial input force exerted forward on the control rod 38. The actuating force is exerted against a return force produced on the rod 38 by a return spring 40 which is interposed between the movable piston 22 and the control rod 38.

The front end of the control rod 38 which is opposite its free end is shaped as a ball joint 42 and is received in a housing 44 complementary to a substantially cylindrical plunger 46 which is slidably mounted in the movable piston 22.

A rear annular seat 48 of the plunger 46 is part of a three-way valve 50 which is capable of varying the second pressure "P ₂ " prevailing in the rear chamber 18, in particular by connecting the front chamber 16 and the chamber rear 18 when the control rod 38 is in the rest position, or by gradually bringing the rear chamber 18 into communication with the atmospheric pressure "P _a " when the control rod 38 is actuated. The operation of the three-way valve 50 being known from the state of the art, it will not be described more explicitly in the present description.

In known manner, a feeler 52, which is slidably mounted on the front end of the plunger 46 which is opposite to the housing 44, is slidably mounted inside a bore 54 of the movable piston 22 which opens facing the cup reaction 30. In this way, the feeler 52 is capable of being urged by the plunger 46 to in turn urge the reaction disc 32 and compress it, which thus makes it possible to transmit to the plunger 46 and, in so doing, to the control rod 38, the reaction force of the master cylinder re 36. The reaction disc 32 transmits the reaction of the master cylinder to the control rod 38 in all cases, both in an extreme position of extreme actuation end of travel of the control rod 38 only in a position for actuating the start of braking of the control rod 38.

In known manner, such a servomotor 10 comprises a device 56 for an unidirectional clutch formed by a tilting key 60 which makes it possible, when the plunger 46 returns, to block a socket 58 which is slidably mounted around the plunger 46 behind the feeler r 52, so that it immobilizes feeler r 52 in contact with the reaction disc 32, which allows me to maintain a maximum effort on the rear face of the movable piston 22 even if the driver would have partially released his effort .

This design has the drawback of requiring the manufacture and adjustment of a socket 58 interposed between the feeler r 52 and the plunger r 46, which considerably increases the cost of manufacturing such a booster 1 0.

Furthermore, the socket 58 being blocked by the key 60 during a rapid return of the plunger r 46 and during a slow return of the plunger 46, the blocking of the socket 58 has effect only during rapid return of the diver 46. As a result, part of the stroke return of the plunger 46 is used in pure loss to activate the release of the one-way clutch device 56.

The invention makes it possible to remedy this drawback by using a unidirectional clutch device 56 that is locked on a socket comprising an integrated feeler as soon as the plunger is actuated, and that i participates in blocking the feeler only when when the diver returns.

A booster according to the invention has been shown according to various embodiments with reference to FIGS. 2a to 2e, 4a to 4th, 6a to 6th, 8a to 8th, and 10a to 10th.

In all the embodiments of the invention, the unidirectional clutch device 56 comprises a key 60 of substantially annular wedging, which surrounds a dou ille 58, whose front end forms the feeler 52, and which is slidably mounted on r the diver r 46.

The jamming key 60 is resiliently recalled by pressing on the casing of the actuator. In particular, as illustrated in FIGS. 2a, 4a, 6a, 8a and 10a, a lower end 62 of the key 60 is, in the rest position of the piston 22, supported on a support element 64 of the casing of the booster 10. This support can be direct, as shown in Figures 2a, 4a, 6a, and 10a or indirect as shown in Figure 8a.

The wedging key 60 is mounted axially with respect to the control piston with a determined clearance which will be described in more detail later with reference to each of the embodiments.

The jamming key 60 is likely, when the input force is applied to the rod 38 and consequently to the plunger 46, to be driven by the control piston 22 to leave its support on the support element 64 of the casing of the servomotor and tilt around a generally transverse axis perpendicular to the axis A of the servomotor r 10 in order to get caught on the periphery of the socket 58, in particular so that when rapid return of the control rod 38 and of the plunger to a speed greater than or equal to the determined speed, the jamming key transmits the reaction from the braking master cylinder to the piston as soon as the determined clearance is absorbed . According to the invention, the probe 52 has come integrally with the socket 58. Thus, the probe 52, which forms the front end of the socket 58, consists of a cylindrical front section of the socket and it is mounted sliding in a complementary bore 54 of the piston 22 which opens into the cup 30 opposite the reaction plate 32.

The socket 58 has a cylindrical rear section 53 which i is of a diameter greater than its section 52 of the front end forming a probe, which is slidably mounted in a rear bore 55 complementary to the piston 22, and which is resiliently biased towards the rear against the plunger 46 by means of a spring 47 bearing on the piston 22.

The plunger 46 is slidably mounted in a bore 69 of the socket 58, a front face 77 of the bottom of which allows the axial support of the plunger 46 in the extreme actuation position of the control rod 38.

The wedging key 60 is mounted in a recess 66 which i passes vertically through the piston, and it has the shape of a substantially radial orientation plate which is crossed by the sleeve 60, the lower end 62 of the key wedge 60 protruding from the socket 58 opposite the support element 64 of the casing, the wedge key 60 being also resiliently recalled - directly or indirectly - against a rear wall of the recess 66.

The rear section 53 of the socket 58 includes a pair of oblong slots 68, shown in Figures 3, 5, 7, 9, and 11, which are oriented substantially along the axial direction and which are diametrically opposite. The plunger r has a transverse bore, coinciding with the oblong slots 68. The transverse bore of the plunger and the oblong slots 68 of the socket 58 are crossed by a transverse pin 70 which i protrudes transversely on either side of the socket ille 58 in particular for cooperating with the wedging key 60 in order to return it to the rest position in abutment on the support element of the actuator casing.

Figures 2a to 2e illustrate a first embodiment of the invention in which the wedging key 60 is recalled by means of a first spring 72 which i is interposed between the front face 74 of the recess 66 and l 'lower end 62 of the key.

In this embodiment, this first spring 72 is tilted back and forth away from the axis A of the booster, so as to favor the tilting of the key 60 on the periphery of the socket 58 when the piston 22 advancing, the lower end 62 of the key 60 leaves its support i on the support element 64.

A second spring 76 is interposed between the rear face 78 of the recess 66 and the upper end 80 of the key 60 for wedging. More particularly, the upper end 80 of the wedging key 60 comprises a pin 82 for centering the second spring.

Furthermore, the pin 70 is arranged in front of the wedging key 60.

As illustrated in FIG. 3, the determined clearance "J" is arranged between a contact face 84 of the upper end 80 of the wedging key 60 and a front contact face 86 of the recess of the piston.

In this configuration, the actuator 10 is capable of occupying different positions which are shown with reference to FIGS 2a to 2e.

From the rest position shown in Figure 2a, the rod 38 can be actuated in a slow application position, shown in Figure 2b. In this configuration, the rod 38 is actuated slowly enough for the piston 22 to move at substantially the same speed as the plunger 46 secured to the rod. The plunger 46 and the socket 58 comprising the feeler 52 move with a stroke less than the clearance "J". The probe 52 requests the reaction plate 32.

The displacement of the piston 22, which drives the key 60, causes the key 60 to tilt, which then gets stuck on the periphery of the sleeve 58 as soon as the lower end of the latter leaves the bearing element 64 of the casing of the booster, absorbing the clearance "J".

When the rod 38 is actuated in a slow application return position, shown in FIG. 2c, the key 60 remains stuck on the periphery of the socket 58 as long as the clearance "J" is not completely consumed and that the lower end 62 of the key 60 is not again brought into contact with the support element 64 of the booster. The socket 58 accompanies the plunger 46 in its return movement.

From the rest position shown in Figure 2a, the rod 38 is capable of being actuated in a quick application position, shown in Figure 2d.

In this configuration, the rod 38 is actuated at a speed faster than the piston 22, due to the delay in balancing the pressure in the rear chamber of the booster. The plunger 46 and the socket 58 comprising the feeler r 52 move with a stroke greater than the clearance "J". The probe 52 enters the reaction disc 32, thereby transmitting the reaction force of the master cylinder to the conductor.

The piston 22 moves with a delay relative to the movement of the plunger 46 and drives the key 60. As a result, it causes the key 60 to tilt, which then gets stuck on the periphery of the socket 58 as soon as the end bottom of the key 60 leaves the support element 64 of the casing of the booster, absorbing the clearance "J". When the rod 38 is actuated in a rapid application return position, as shown in FIG. 2e, the key 60 remaining wedged on the periphery of the socket 58, the socket 58 and the feeler 52 first accompany the plunger on a return stroke equal to the clearance J, the feeler 52 always transmitting to the rod 38 the reaction of the master cylinder by means of the reaction plate 32. Once this race has been completed, the key 60, which is still blocked on the sleeve 60, has run through ru in the opposite direction a distance equal to the clearance "J" according to which it is mounted in the body 22. At this moment, it again comes into contact with the body of the piston 22, and it thus blocks the socket 58 and the probe 52, which makes it possible to maintain the application of a maximum braking force to the master cylinder. The plunger 46 continues its return stroke but is no longer accompanied by the socket 58 and by the feeler 52. This configuration lasts as long as the plunger has not traversed in reverse the remaining part of its initial stroke, it ie a distance equal to the difference of its initial stroke and the clearance "J".

When the key 60 comes into contact with the support element i 64 of the casing of the servomotor, the latter brings the plunger 46 back via the pin 70.

Figures 4a to 4e and 5 illustrate a second embodiment of the invention in which the wedging key 60 is recalled by means of a single spring 72 which i is interposed between the front face 74 of the recess 66 and the lower end 62 of the key.

In a manner analogous to the previous embodiment, this spring 72 is inclined back and forth away from the axis A of the booster, so as to promote the tilting of the key 60 on the periphery of the socket 58 when , the piston 22 advancing, the lower end 62 of the key 60 leaves its support on the support element 64.

Furthermore, the pin 70 is arranged in front of the wedging key 60. As illustrated in FIGS. 4a, the determined clearance "J" is arranged between a contact face 84 of the upper end 80 of the wedging key 60 and the end 88 of a fixed axial finger

90 which passes through a bore 92 of the piston 22 and projects from the front face 74 of the recess 66 of the piston 22.

The fixed axial finger 90 can for example be arranged in a determined axial position in the bore 92 of the piston 22 so as to allow an adjustment of the clearance "J". For example, and in a nonlimiting manner of the invention, the axial finger can be force-fitted, or else be screwed, into the bore 92 according to a determined axial position with a view to obtaining a determined clearance "J" .

In this configuration, the operation of the booster 10 is substantially similar to that of the booster as described in the previous embodiment.

From the rest position shown in Figure 4a, the rod 38 can be actuated su iving a position of slow application, shown in Figure 4b.

In this configuration, the rod 38 is actuated slowly enough for the piston 22 to move at substantially the same speed as the plunger 46 secured to the rod. The plunger 46 and the socket 58 comprising the feeler 52 move with a rse less than the clearance "J". The feeler 52 urges the reaction plate 32. The displacement of the piston 22, which drives the key 60, causes the key 60 to tilt, which then becomes jammed on the periphery of the socket 58 as soon as the lower end of the latter leaves the bearing element 64 of the booster casing, absorbing the clearance "J", the key coming 60 into contact with the end 88 of the axial finger 90.

When the rod 38 is actuated in a position for re-application of slow application, shown in FIG. 4c, the key 60 remains stuck on the periphery of the socket 58 as long as the clearance "J" is not completely consumed and that the lower end re 62 of the key 60 is not again brought into contact with the support element 64 of the booster. The socket 58 accompanies the plunger 46 in its return movement.

From the rest position shown in Figure 4a, the rod 38 is capable of being actuated in a position of rapid application, shown in Figure 4d.

In this configuration, the rod 38 is actuated at a speed faster than the speed of movement of the piston 22, due to the delay in balancing the pressure in the rear chamber of the booster. The plunger 46 and the socket 58 comprising the feeler 52 move with a stroke greater than the clearance "J". The probe 52 enters the reaction plate 32, thereby transmitting the reaction force of the master cylinder to the driver. The piston 22 moves with a delay relative to the displacement of the plunger r 46 and drives the key 60. As a result, it causes the key 60 to tilt, which then gets stuck on the periphery of the socket 58 as soon as the lower end of the key 60 leaves the support element 64 of the casing of the booster, absorbing the clearance "J", that is to say by coming into abutment on the end 88 of the axial finger 90.

When the rod 38 is actuated in a fast application return position, as shown in Figure 4e, the key 60 remaining stuck on the periphery of the socket 58, the socket 58 and the probe 52 first accompany the plunger on a return stroke equal to the clearance "J", the feeler r 52 still transmitting to the rod 38 the reaction of the master cylinder via the reaction disc 32. Once this course is completed or on the street, the key 60, qu i is still blocked on the dou ille 60, has traveled in the opposite direction a distance equal to the clearance "J" according to which it is mounted relative to the axial finger 90. At this time, it again comes into contact with the body of the piston 22, and it thus blocks the socket 58 and the probe 52, which allows to maintain the application of a maximum braking force to the master cyl indre. The plunger 46 continues its return stroke but is no longer accompanied by the dou ille 58 and by the feeler 52. This configuration lasts as long as the plunger has not traversed in reverse the remaining part of its initial stroke, c 'is to say a distance equal to the difference of its initial race and the game "J".

When the key 60 comes into contact with the support element 64 of the casing of the actuator, the latter brings the plunger 46 back via the pin 70.

FIGS. 6a to 6e and 7 illustrate a third embodiment of the invention in which the wedging key 60 is recalled by means of a single spring 72 which is interposed between the front face 74 of the recess 66 and the lower end 62 of the key.

In a manner analogous to the previous embodiments, this spring 72 is inclined from front to back away from the axis A of the servomotor, so as to favor the tilting of the key 60 on the periphery of dou ille 58 when , the piston 22 advancing, the lower end 62 of the key 60 leaves its support on the support element 64. In addition, the gou pil le 70 is arranged in front of the key

60 of jamming.

In this embodiment, the upper end 80 of the wedging key 60 is slidably mounted with a radial clearance on a fixed axial finger 94 which i passes through a bore 96 of the piston 22 and protrudes from a front face 76 of the recess 66 of the piston 22, and a leaf spring 98 is arranged between the axial finger 94 and the upper end 80 of the key 60 for wedging. Advantageously, the leaf spring 98 has substantially the shape of a U, one branch of which is mounted in a jumper on the axial finger 94 and the other branch of which, crossed by the finger 94, bears on the upper end 80 of the jamming key 60.

In this third embodiment, the determined clearance corresponds to the sliding stroke of the upper end 80 of the key 60 for wedging on the finger 94. From the rest position shown in Figure 6a, the rod 38 can be actuated in a slow application position, shown in Figure 6b.

In this configuration, the rod 38 is actuated slowly enough for the piston 22 to move at substantially the same speed as the plunger 46 secured to the rod. The plunger r 46 and the socket 58 comprising the feeler 52 move with a stroke less than the sliding stroke of the upper end 80 of the key 60 for wedging on the finger 94. The feeler 52 urges the reaction disc 32.

The displacement of the piston 22, which drives the key 60, causes the key 60 to tilt, which then gets stuck on the periphery of the sleeve 58 as soon as the lower end of the latter leaves the bearing element 64 of the casing of the booster, absorbing the sliding rse of the upper end 80 of the key 60 for wedging on the finger 94 corresponding to the determined clearance.

When the rod 38 is actuated in a slow application return position, shown in FIG. 6c, the key 60 remains wedged on the periphery of the socket 58 as long as the clearance corresponding to the sliding stroke of the upper end 80 of the key 60 wedging on the finger 94 is not completely consumed and that the lower end 62 of the key 60 is not again returned to contact with the support element 64 of the booster. The socket 58 accompanies the plunger 46 in its return movement.

From the rest position shown in Figure 6a, the rod 38 is capable of being actuated su iving a position of rapid application, shown in Figure 6d. In this configuration, the rod 38 is actuated at a speed faster than the speed of movement of the piston 22, due to the delay in balancing the pressure in the rear chamber of the booster. The plunger 46 and the socket 58 comprising the probe 52 move with a stroke greater than the sliding stroke of the upper end 80 of the key 60 for wedging on the finger 94. The probe 52 penetrates into the reaction disc 32, thus transmitting to the conductor the reaction force of the master cylinder. The piston 22 moves with a delay relative to the movement of the plunger 46 and drives the key 60. As a result, it causes the key 60 to tilt, which then gets stuck on the periphery of the socket 58 as soon as the end lower part of the key 60 leaves the support element 64 of the casing of the booster, absorbing the determined play, that is to say coming into abutment at the bottom of the neck on the axial finger 94.

When the rod 38 is actuated in a fast application return position, as shown in FIG. 6e, the key 60 remaining wedged on the periphery of the socket 58, the socket 58 and the feeler 52 first accompany the plunger r on a return stroke r equal to the sliding stroke of the upper end 80 of the key 60 wedging on the finger 94. This is made possible by the fact that the upper end 80 of the key 60 is mounted with a radial clearance on the finger 94, the key 60 sliding on the finger 94 while remaining tilted. The feeler 52 always transmits the reaction of the master cylinder to the rod 38 via the reaction disc 32. Once this race has been completed, the key 60, which is still blocked on the dou ille 60, has traveled in the direction reverses a distance equal to its sliding stroke on the finger 94 in the body 22. At this time, it again comes into contact with the body of the piston 22, and it thus blocks the socket 58 and the probe 52, which allows maintain the application of a maximum braking force to the master cylinder. The plunger 46 continues its return stroke but is no longer accompanied by the socket 58 and by the feeler 52. This configuration lasts as long as the plunger has not traversed in reverse the remaining part of its initial stroke, it ie a distance equal to the difference of its initial stroke and the sliding stroke of the key 60 on the finger 94. When the key 60 comes into contact with the support element 64 of the casing of the booster, the latter brings back the plunger 46 by means of the pin 70.

FIGS. 8a to 8e and 9 illustrate a fourth embodiment of the invention in which the wedging key 60 is recalled by means of a single spring 100 which is interposed between the front face 74 of the recess 66 and the lower end 62 of the key.

Unlike the previous embodiments, this first spring 1 00 is of axial orientation.

Furthermore, the actuator r 10 includes an additional trigger key 102 which is mounted behind the key 60 for wedging in the recess 66.

The additional key 102 for triggering has the form of a substantially radial orientation plate which is traversed by the socket 58, the lower end 1 04 of which protrudes from the socket 58 and is interposed between the lower end 62 of the wedging key 60 and the element 64 for supporting the envelope. An upper end 106 of the additional trigger key 102 is coupled by means of an elastic coupling device 108 to the upper end 80 of the wedging key 60.

More particularly, the elastic coupling device 108 comprises a jumper 1 10 which encloses the upper end 80 of the wedging key 60 and of which a lug 1 12 extending towards the rear crosses the upper end 106 of the key 1 02 trigger and carries a spring 1 14 interposed between the jumper 1 1 0 and the upper end 106 of the key 102 trigger.

As a result, the determined clearance "J" is arranged between the rear end of the jumper 110 and the outer end 106 of the release key 102, and it corresponds substantially to the compression stroke of the spring 114. In this fourth embodiment, the pin 70 is arranged between the key 60 for jamming and the key 102 for triggering, so as to allow the recall of the key 60 for wedging by means of the key 102 for triggering. From the rest position shown in Figure 8a, the rod 38 can be actuated in a slow application position, shown in Figure 8b.

In this configuration, the rod 38 is actuated slowly enough for the piston 22 to move at substantially the same speed as the plunger 46 secured to the rod. The plunger 46 and the socket 58 comprising the feeler 52 move with a stroke less than the clearance "J" determined arranged between the jumper 1 10 and the upper end 106 of the key 102 trigger. The probe 52 urges the reaction disc 32.

The displacement of the piston 22, which drives the trigger key 102, causes the key 102 to tilt, which, once the clearance "J" has been absorbed, allows the key to tilt

60 jamming by release of the lower end thereof. The key 60 then gets stuck on the periphery of the socket 58.

When the rod 38 is actuated in a slow application return position, shown in FIG. 8c, the key 60 remains stuck on the periphery of the socket 58 as long as the lower end 104 of the trigger key 102 n 'is not returned again in contact with the support element i 64 of the actuator. The socket 58 accompanies the plunger 46 in its return movement.

From the rest position shown in Figure 8a, the rod 38 can be actuated in a quick application position, shown in Figure 8d.

In this configuration, the rod 38 is actuated at a speed faster than the speed of movement of the piston 22, due to the delay in balancing the pressure in the rear chamber of the booster. Diver 46 and Dou ille 58 comprising the probe 52 move with a stroke greater than the clearance "J" arranged between the jumper 1 10 and the upper end 106 of the key 102 trigger. The probe 52 enters the reaction disc 32, thereby transmitting the reaction force of the master cylinder to the conductor.

The piston 22 moves with a delay relative to the displacement of the plunger 46 and drives the trigger key 102. As a result, it causes the key 60 to tilt, which then gets stuck on the periphery of the socket 58 as soon as the game "J" is absorbed.

When the rod 38 is actuated in a fast application return position, as shown in FIG. 8e, the key 60 remaining wedged on the periphery of the socket 58, the socket 58 and the feeler 52 first accompany the plunger on a return rse equal to the clearance "J". The probe 52 always transmits the reaction of the master cylinder to the rod 38 via the reaction plate 32. Once this stroke has been traveled, the trip key 102 has traveled in the opposite direction a distance equal to the clearance "J" determined. At this time, it again comes into contact with the body of the piston 22, and it thus blocks the socket 58 and the probe 52 by means of the wedging key 60, which allows the application of maximum braking force on the master cylinder. The plunger 46 for resumes its retouching stroke but is no longer accompanied by the socket 58 and by the probe 52. This configuration lasts as long as the plunger has not traversed in the opposite direction the remaining part of its initial stroke, ie a distance equal to the difference of its initial stroke and the clearance "J".

When the key 102 comes into contact with the support element 64 of the casing of the booster, the latter brings back the plunger 46 by means of the pin 70. As a result, the trigger key 102 pushes the key 60 jamming through the coupling device 108, which causes the jamming key 60 to return to the rest position. Figures 10a to 10e and 1 1 illustrate a fifth embodiment of the invention in which the piston 22 is made in two parts and comprises a body 1 16 inside which is slidably mounted and returned to the rear a cartridge 1 18 cylindrical. In particular, the cartridge 1 18 is mounted in a bore 121 of the body 1 16 of the piston, which bore is closed at its front end by a plug 123. The cartridge 1 18 is biased elastically towards the rear by a spring 1 19 which is supported on the stopper 123. The stopper 123 is for example screwed on the body 1 1 6 of the piston 22. the cartridge 1 18 slidably receives the socket 58, which is biased elastically backwards in the cartridge 1 18 via spring 47.

The body 1 16 and the cartridge 1 18 are each perforated to form the recess 66 receiving the key 60 whose lower end re 62 protrudes from the body 1 16 opposite the support element 64 of the envelope .

A first spring 120 is interposed in the cartridge between the front face of the recess 66 and the upper end 80 of the wedging key 60, and an additional plate-shaped trigger key 122 is mounted in jumper on the cartridge 1 18, simultaneously pressing on the rear of the upper end 80 of the key 60 wedging. The additional trigger key 122 is recalled elastically towards the front with respect to the body 116 of the piston by means of a second spring 124.

Furthermore, the pin 70 is arranged in front of the wedging key 60.

In this fifth embodiment, the determined clearance corresponds to the stroke of the cartridge 1 18 in the body 1 1 6 of the piston 22.

From the rest position shown in Figure 10a, the rod 38 can be actuated in a slow application position, shown in Figure 10b. In this configuration, the rod 38 is actuated slowly enough for the piston 22 to move at substantially the same speed as the plunger r 46 secured to the rod. The plunger 46 and the socket 58 comprising the feeler 52 move with a stroke less than the sliding stroke of the cartridge 1 18 in the body 1 16 of the piston 22. The feeler 52 urges the reaction disc 32.

The displacement of the piston 22, which drives the cartridge 1 16 and the trigger key 122 in abutment on the wedging key 60, causes the tilting key 60 to tilt, which then gets stuck on the periphery of the socket 58.

When the rod 38 is actuated in a slow application return position, shown in FIG. 10c, the key 60 remains wedged on the periphery of the socket 58 as long as the lower end 62 of the trigger key 60 does not is not returned again in contact with the support element i 64 of the actuator. The socket 58 accompanies the plunger 46 in its return movement.

From the rest position shown in Figure 10a, the rod 38 is capable of being actuated in a position of rapid application, shown in Figure 10d.

In this configuration, the rod 38 is actuated at a speed faster than the speed of movement of the piston 22, due to the delay in balancing the pressure in the rear chamber of the booster. The plunger 46 and the socket 58 comprising the feeler 52 move with a stroke greater than the clearance "J" arranged between the cartridge 1 16 and the body 1 18 of the piston 22. The feeler 52 penetrates into the reaction disc 32, thus transmitting to the driver the reaction force of the master cylinder ind re.

The piston 22 moves with a delay relative to the movement of the plunger r 46 and drives the trigger key 1 22. As a result, it causes the key 60 to tilt, which is then wedges on the periphery of the socket 58 as soon as the clearance "J" is absorbed.

When the rod 38 is actuated in a fast application return position, as shown in Figure 1 0e, the key 60 remaining stuck on the periphery of the socket 58, the socket 58 and the probe 52 first accompany the plunger on a return stroke equal to the game "J". The probe 52 always transmits the reaction of the master cylinder to the rod 38 via the reaction disc 32. Once this race has been completed, the trigger key 122 has traveled in the opposite direction for a distance equal to the determined clearance "J". At this time, it again compresses the spring 124 which is interposed between the trigger key 122 and the body 1 16 of the piston 22, and it thus blocks the socket 58 and the probe 52 by means of the wedging key 60 , which makes it possible to maintain the application of a maximum braking force to the master cylinder. The plunger 46 continues its return stroke but is no longer accompanied by the socket 58 and by the probe 52. This configuration lasts as long as the plunger has not traversed in reverse the remaining part of its initial stroke, it is to say a distance equal to the difference of its initial race and the game "J".

When the plunger 46 has returned to its initial position, the pin 70 and the end 62 of the jamming key 60 come into contact, which causes the jamming key 60 to return to the rest position.

The invention therefore advantageously makes it possible to benefit from a maximum braking force in emergency braking situations, whatever the behavior of the driver after violent braking.

Claims

REVEN DICATIONS 1. Pneumatic brake booster (10) for a motor vehicle, of the type which includes a rigid casing (12) inside which is movable a transverse partition (14) delimitably sealing a front chamber (16), subjected to a first pressure (Pi) of engine depression, and a rear chamber (18) subjected to a second pressure (P ₂ ) varying between engine depression and atmospheric pressure (P _a ), of the type which includes a movable piston ( 22) for actuating a master cylinder (36) for braking the vehicle, integral with the movable partition (14), and of the type which comprises a control rod (38) which is capable of moving in the piston (22), selectively between a rest position and an extreme actuation position as a function of an axial input force exerted towards the front against a return force exerted on the rod (38 ) by a return spring (40), of the type which includes a plunger r (46) q ui is arranged at the front of the control rod (38) in the piston (22), of the type which comprises a three-way valve (50) which comprises at least one annular seat (48) rear of the plunger (46) and which is capable of varying the second pressure (P ₂ ) prevailing in the rear chamber (18), in particular by bringing the front chamber (16) and the rear chamber (18) into communication when the control rod (38) is in the rest position or by gradually bringing the rear chamber (18) into communication with the atmospheric pressure (P _a ) when the control rod (38) is actuated to cause displacement of the piston (22), of the type in which, in the extreme actuation position of the control rod (38), a feeler (52) forming the front end of a sleeve (58) slidably mounted at the front end of the plunger (46) is biased by the plunger (46) in contact with a reaction disc (32) integral with the rear face of the movable piston (22) for transmitting to the plunger (46) and to the control rod (38) the reaction force which i is transmitted from the master cylinder (36) of the vehicle to the movable piston (22), and of the type in which, when the control rod (38) is actuated or released at a determined speed that i is greater than that of the balancing of the second pressure (P ₂ ) in the rear chamber (18 ) of the servomotor (10), the control rod (38) and the plunger (46) move faster than the piston (22), characterized in that it comprises a one-way clutch device (56) which comprises a key (60) substantially annular wedging, which surrounds the dou ille (58), which is resiliently returned to bear on the casing (12) of the actuator, which is mounted axially relative to the piston (22) control with a game (J) determined, and which is likely, when the input force is applied, to be driven by the control piston (22) to leave its support (64) on the casing (12) of the booster (10 ) and tilt around a generally transverse axis in order to get stuck on the periphery of the socket (58), in particular d e so that during a rapid return of the control rod (38) and the plunger (46) at a speed greater than or equal to the determined speed, the wedging key (60) transmits the reaction of the master cylinder (36 ) braking the piston (22) when the determined clearance (J) is absorbed.

2. Booster (10) according to the preceding reselling ication, characterized in that the feeler (52) forming the front end of the sleeve (58) consists of a cylindrical front section of the sleeve (58) which is mounted sliding in a front bore (54) complementary to the piston (22).

3. Pneumatic booster (10) according to the preceding claim, characterized in that the sleeve (58) has a cylindrical rear section (53) which is of a diameter greater than its front end section (52) forming probe, which is slidably mounted in a rear bore (55) complementary to the piston (22), and which is biased elastically towards the rear against the plunger (46) by means of a spring (47) bearing on the piston (22).

4. Pneumatic actuator (10) according to any one of the preceding claims, characterized in that the plunger r (46) is slidably mounted in a bore (69) of the sleeve (58) including a front face (77) bottom allows the axial support of the plunger r (46) in the extreme actuation position of the control rod (38).

5. Pneumatic booster (10) according to the preceding claim, characterized in that the key (60) of wedging is mounted in a recess (66) which vertically passes through the piston (22), and in that it has the form of 'a substantially radial orientation plate which is traversed by the sleeve (58), a lower end (62) of the wedging key projecting out of the sleeve opposite a support element i (64) of the 'envelope 12), the wedging key (60) being furthermore elastically recalled against a rear wall of the recess (62).

6. Pneumatic booster (10) according to one of claims 3 to 5, characterized in that the rear section (53) of the sleeve comprises a pair of diametrically opposite oblong lights (68) with an axial orientation and in that the plunger (46) has a transverse hole, coinciding with the oblong slots (68), which are crossed by a transverse pin (70) which projects transversely on either side of the socket (58) in particular for cooperating with the key (60) jamming in order to return it to the rest position pressing on the support element i (64) of the casing (12) of the servomotor (1 0).

7. Booster (10) according to the preceding claim, characterized in that a first spring (72, 100) is interposed between the front face of the recess (66) and the lower end (62) of the key jamming.

8. Booster (10) according to one of claims 6 or 7, characterized in that the pin is arranged in front of the key (60) of jamming.

9. R actuator (10) according to the preceding claim, characterized in that the first spring (72) is tilted back and forth away from the axis (A) of the servomotor (10).

1 0. Booster (10) according to the preceding claim, characterized in that a second spring (76) is interposed between the rear face of the recess (66) and the upper end (80) of the key (60) of jamming.

1 1. Booster (10) according to the preceding claim, characterized in that the upper end (80) of the wedging key comprises a pin (82) for centering the second spring (76).

1 2. Booster (10) according to one of claims 10 or

1 1, characterized in that the determined clearance (J) is arranged between a contact face (84) of the upper end (80) of the locking key (60) and a front contact face (86) of the 'recess (66) of the piston (22).

1 3. Booster (10) according to claim 9, characterized in that the clearance (J) determined is arranged between a face (84) of contact of the upper end (80) of the key (60) jamming and l end (88) of a fixed axial finger (90) which passes through the piston (22) and projects out from a front face (74) of the recess (66) of the piston (22).

14. Booster (10) according to claim 9, characterized in that the upper end (80) of the wedging key is slidably mounted with a radial clearance on a fixed axial finger (94) which passes through the piston (22) and protrudes from a front face of the recess (66) of the piston (22), and in that a leaf spring (98) is arranged between the axial finger and the upper end (80) of the jamming key (60).

1 5. Booster (1 0) according to the preceding claim, characterized in that the determined clearance corresponds to the stroke of sliding of the end on peri re (80) of the key (60) of wedging on the finger (94).

16. Booster (10) according to claim 7, characterized in that the first spring (100) is of axial orientation.

1 7. Booster (10) according to the preceding claim, characterized in that it comprises a key (102) additional trigger which is mounted behind the key (60) wedging in the recess (66), which has the shape a substantially radial orientation plate which is traversed by the sleeve (58), the lower end (104) of which protrudes from the sleeve (58) and is interposed between the lower end (62) of the wedge key (60) and the support element (64) of the casing (12), the upper end of which is coupled by means of an elastic coupling device (108) at the end upper (80) of the jamming key (60).

1 8. Booster (10) according to the preceding claim, characterized in that the device (108) for elastic coupling comprises a jumper (1 10) which encloses the upper end (80) of the key (60) of jamming and a lug (1 12) extending towards the rear crosses the upper end of the release key (102) and carries a spring (1 14) interposed between the jumper (1 10) and the upper end of the trigger key (102).

19. Booster r (10) according to the preceding claim, characterized in that the determined clearance is arranged between the rear end of the jumper (1 10) and the upper end of the key (102) trigger.

20. Servo r (10) according to one of claims 1 7 to 1 9, characterized in that the pinning pin (70) is arranged between the key (60) jamming and the key (102) trigger, to recall the key (60) jamming through the key (102) trigger.

21. Booster (10) according to claim 6, characterized in that the piston (22) is made in two parts and comprises a body (1 16) inside which is slidably mounted and biased towards the rear a cylindrical cartridge (1 18) which slidably receives the sleeve (58), the body (1 16) and the cartridge (1 18 ) each being perforated to form the recess (66) receiving the key (60) of wedging, a lower end (62) protruding from the body (1 1 6) opposite a support element (64) of the casing (12), a first spring (120) being interposed in the cartridge (1 18) between the front face of the recess (66) and the upper end (80) of the key (60) for wedging, and an additional key (122) in the form of a plate, mounted in a jumper on the cartridge (1 18) bearing on the rear of the upper end (80) of the wedging key (60) and being recalled elastically forward relative to the body (1 16) of the piston via a second spring (124).

22. Booster (10) according to the preceding claim, characterized in that the determined clearance corresponds to the stroke of the cartridge (1 18) in the body (1 16) of the piston.