Patent Grant
7178882
The invention disclosed in this application relates to the general subject matter of brake boosters and in particular the brake booster disclosed in co-pending U.S. patent application Ser. No. 10/1542,097 filed on Jul. 13, 2005.
The invention relates to a boosted brake for a motor vehicle.
The invention relates more particularly to a boosted brake for a motor vehicle, of the type which comprises a pneumatic brake booster actuating a master cylinder, of the type in which the booster comprises a rigid casing inside which can move a transverse partition sealably delimiting a front chamber subjected to a first pressure and a rear chamber subjected to a second pressure varying between the first pressure and a pressure greater than the first pressure, of the type in which the booster comprises a moving piston fixed to the moving partition and comprising a front face which can act on a primary piston of the master cylinder by way of a reaction disk housed in a cage interposed between the moving piston and the primary piston, of the type in which the booster comprises a control rod which moves in the piston selectively as a function of an axial input force exerted forward against a return force exerted on the rod-by a return spring, of the type in which the booster comprises a plunger which is arranged in front of the control rod in the piston and which comprises at its rear, end at least one annular rear seat of a three-way valve which can move progressively between a position in which, with the control rod at rest, the front chamber and the rear chamber are in communication, and a position in which, with the control rod actuated, the second pressure prevailing, in the rear chamber increases, the valve placing the rear chamber in communication with the pressure which is greater than the first pressure, and of the type in which the booster comprises a feeler, forming the front end of the plunger and passing through a bore leading from the piston, which, when the control rod is in the rest position, is arranged at a defined jump distance from the reaction disk and which is able, when the control rod is actuated with an input force whose intensity is greater than a first defined intensity, to come into contact with the reaction disk in such a way as to transmit to the plunger and to the control rod the reaction force of the master cylinder, the ratio of the area of the reaction disk in contact with the cage to the area of the feeler in contact with the reaction disk defining a first defined boost ratio, and of the type in which the cage comprises at least one moving decompression wall which, when the control rod is actuated with an input force whose intensity is greater than a second defined intensity greater than the first, is able to move so as to create in the cage an additional volume in which a front part of the reaction disk is able to expand in order to reduce the reaction force transmitted to the feeler by way of the rear face of the reaction disk, the ratio of the area of the reaction disk in contact with the cage to the area of the feeler in contact with the reaction disk defining a second boost ratio, which is greater than the first.
Many examples of boosted brakes of this type are known.
In such a boosted brake, the moving decompression wall generally forms part of a device which is attached to the cage and which is interposed between the reaction disk and the primary piston of the master cylinder.
This device conventionally consists of a housing having one face attached to the reaction disk, this face being drilled to allow the passage of a cylindrical decompression piston which, for its part, is also arranged in contact with the reaction disk. The decompression piston is returned elastically toward the reaction disk by a helical spring which is housed inside the housing and which has substantially the same diameter as the decompression piston. When the intensity of the input force exceeds the second defined value, the decompression piston is pushed back in the housing, compressing the helical spring, and it thus creates a free volume which allows the reaction disk to be decompressed.
This design has many disadvantages in terms of space requirement.
Specifically, this design entails the use of a helical spring which has substantially the same diameter as the decompression piston. It is therefore impossible to reduce the diameter of the helical spring without reducing the diameter of the decompression piston which, as a result, would no longer have an appropriate surface area for creating in the cage a decompression volume sufficient to bring about suitable decompression of the reaction disk.
Conversely, the use of a decompression piston of suitable size does not make it possible to use a helical spring of sufficiently small diameter for the housing to be able, for example, to be housed in the primary piston of the master cylinder.
To overcome this disadvantage, the invention provides a boosted brake comprising a decompression piston of large surface area which is able to create a suitable decompression volume for the reaction disk and nevertheless allows the use of a helical spring of small size.
To this end, the invention provides a boosted brake of the above-described type, characterized in that the primary piston of the master cylinder is arranged in contact with the reaction disk and in that it comprises:
According to other features of the invention:
Other features and advantages of the invention will become apparent on reading the detailed description which follows and which will be understood by referring to the appended drawing in which.
In the description which will follow identical reference numbers denote components which are identical or have similar functions.
By convention, the terms “front” “rear” “upper” and “lower” respectively denote elements or positions which are respectively directed toward the left, the right, the top or the bottom of the figures.
In a known way, the boosted brake 10 comprises a pneumatic brake booster 12 which is intended to activate a master cylinder 14.
The booster 12 comprises a rigid casing 16 inside which can move a transverse partition 18 sealably delimiting a front chamber 20 subjected to a first pressure “P1” and a rear chamber 22 subjected to a second pressure “P2” varying between the first pressure “P1” and a pressure “Pa” which is greater than the first pressure “P1”.
In a known way, the booster 12 comprises a moving piston 24 fixed to the moving partition 18 and comprising a front face 26 which is able to act on a primary piston of the master cylinder 14 by way of a reaction disk 28. The reaction disk 28 is housed in a cage 30 which is interposed between the moving piston 24 and the primary piston (not shown).
The booster 12 also comprises a control rod 32 which moves in the piston 24 selectively as a function of an axial input force exerted toward the front against a return force exerted on the rod 32 by a return spring 34.
The booster 12 comprises a plunger 36 which is arranged in front of the control rod 32 in the piston 24 and which comprises at its rear end 38 at least one annular rear seat of a three-way valve 40 which can move progressively between a position in which, with the control rod 32 at rest, the front chamber 20 and the rear chamber 22 are in communication, and a position in which, with the control rod 32 actuated, the second pressure “P2” prevailing in the rear chamber 22 increases, the valve 40 placing the rear chamber 22 in communication with the pressure “Pa” which is greater than the first pressure “P1”.
The booster 12 comprises a feeler 42, arranged at the front end of the plunger 36 and passing through a bore 44 leading from the piston 24, which, when the control rod 32 is in the rest position, is arranged at a defined jump distance from the reaction disk 28 and which is able, when the control rod 32 is actuated with an input force whose intensity is greater than a first defined intensity, to cross over the jump distance and come into contact with the reaction disk 28 in such a way as to transmit the reaction force of the master cylinder 14 to the plunger 36 and to the control rod 32.
In this configuration, the ratio of the area of the reaction disk 28 in contact with the cage 30 to the area of the feeler 42 in contact with the reaction disk 28 in a known way defines a first defined boost ratio.
The disadvantage of this known design is that when the control rod is actuated rapidly with an input force whose intensity is greater than the first defined intensity, the delay in the balancing of the pressures between the front chamber 20 and rear chamber 22 does not allow the moving piston 24 to sufficiently boost the driver's braking force, which must, moreover, overcome the reaction force that the master cylinder 14 exerts on the rod 32 by way of the reaction disk 28.
To overcome this disadvantage, a boosted brake 10 (not shown) of the type described above has been provided in which the cage 30 comprises at least one moving decompression wall which, when the control rod 32 is actuated with an input force whose intensity is greater than a second defined intensity greater than the first, is able to move so as to create in the cage 30 an additional volume in which a front part of the reaction disk 28 is able to expand with respect to the feeler 42.
In this way, a rear part of the reaction disk 28 is able to decompress locally at the level of the feeler 42, which makes it possible to reduce the reaction force transmitted to the feeler 42 by way of the rear face of the reaction disk.
Moreover, in this configuration, since the area of the feeler 42 in contact with the reaction disk is small, the defined boost ratio increases. This second boost ratio is therefore greater than the first.
In such a boosted brake, the moving decompression wall generally forms part of a decompression device which is attached to the cage and which is interposed between the reaction disk and the primary piston of the master cylinder.
This boosted brake (not shown) conventionally comprises a housing fixed to an actuating rod connected to a primary piston of the master cylinder, one face of which housing is attached to the reaction disk and is drilled to allow the passage of a cylindrical decompression piston which, for its part, is also arranged in contact with the reaction disk. The decompression piston is returned elastically toward the reaction disk by a helical spring which is housed inside the housing and which has substantially the same diameter as the decompression piston. When the intensity of the input force exceeds the second defined value, the decompression piston is pushed back in the housing, compressing the helical spring, and it thus creates a free volume which allows the reaction disk to be decompressed.
This design has many disadvantages in terms of space requirement.
Specifically, this design entails the use of a helical spring which has substantially the same diameter as the decompression piston. It is therefore impossible to reduce the diameter of the helical spring without reducing the diameter of the decompression piston which, as a result, would no longer have an appropriate surface area for creating in the cage a decompression volume sufficient to bring about suitable decompression of the reaction disk.
Conversely, the use of a decompression piston of suitable size does not make it possible to use a helical spring of sufficiently small diameter for the housing to be able, for example, to be integrated in the primary piston of the master cylinder.
To overcome this disadvantage, as illustrated in
In a known way, the boosted brake 10 is provided with a cage 30, formed in the piston 24, at least one moving decompression wall 46 of which cage is able, when the control rod 32 is actuated with an input force whose intensity is greater than a second defined intensity greater than the first, to move so as to create in the cage 30 an additional volume in which a front part 48 of the reaction disk 28 is able to expand in order to reduce the reaction force transmitted to the feeler 42 by way of the rear face 50 of the reaction disk 28.
More particularly, according to the invention and as illustrated in
It will be understood that these arrangements in no way restrict the invention and that the piston 62 could comprise a greater number of branches 64, for example 4, 5 or 6 radial branches 64.
As illustrated in
In this way, the boosted brake 10 provides a decompression piston 62 of maximum transverse size “E” and a helical spring 70 of a minimum diameter tailored to the diameter of the primary piston 54 of the master cylinder 14.
It will be understood that the front section 66 and rear section 56 are associated with the bore 68 and the opening 60, respectively, and that they are not necessarily mechanically independent. Thus, in the preferred embodiments of the invention, the primary piston 54 comprises a tubular front part 67 which comprises one part of the front section 66 and which accommodates a rear part 57 which internally comprises the other part of the front section 66, comprising the other part of the bore 68, and the rear section 56.
More specifically, as illustrated in
The face 74, arranged at the end of the opening 60, is arranged angularly between two successive branches 64 of the decompression piston 62 and it projects transversely inside the bore 68. Thus, the rear part 57 associated with the piston 62 having two branches 64 as shown in
Moreover, as illustrated in
As illustrated in
In the configurations described with reference to the first and second embodiments of the invention, the faces 78 are distributed over all the branches 64 of the piston 62. The piston 62 of
The spring 70 may bear directly on the face 78, but the primary piston 54 preferably comprises a bearing washer 79 which is fitted between the helical spring 70 and the bearing face 78 of the decompression piston 62. This washer 79 has an outside diameter corresponding to that of the bore 68 of the front section 66 and it has an inside diameter corresponding to that of the return rod 72 of the decompression piston 62.
Thus, when the piston 62 occupies its rear position as shown in
In this way, the moving wall 46 can move as represented in
In an initial position represented in
In an intermediate position represented in
In the decompression position represented in
Advantageously, as illustrated in
In the first and second embodiments, the front part 67 is fitted, as represented in
As an alternative (not shown), the front part 67 could be tightly fitted in a front end bore of the rear part 57. In that case, the preload of the spring 70 would be defined by the depth of the fit, which would then be limited by a key housed at the bottom end of said bore.
The invention therefore makes it possible to benefit from a moving decompression wall 46 integrated with the primary piston 54 of the master cylinder 14, which makes it possible in particular to facilitate assembly of the boosted brake 10 comprising a master cylinder 14 provided with such a moving wall 46.
| Number | Date | Country | Kind |
|---|---|---|---|
| 03 00885 | Jan 2003 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2004/000620 | 1/26/2004 | WO | 00 | 7/13/2005 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2004/067346 | 8/12/2004 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6082109 | Simon Bacardit | Jul 2000 | A |
| 6092453 | Preker | Jul 2000 | A |
| 6318081 | Bacardit | Nov 2001 | B1 |
| 6931979 | Bacardit et al. | Aug 2005 | B2 |
| 20030056642 | Kobayashi | Mar 2003 | A1 |
| 20060055236 | Barthomieu et al. | Mar 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 19917281 | Oct 2000 | DE |
| 10113292 | Sep 2002 | DE |
| 2820388 | Aug 2002 | FR |
| Number | Date | Country | |
|---|---|---|---|
| 20060038440 A1 | Feb 2006 | US |
