Patent Application
20090212621
This application is the U.S. national phase application of PCT International Application No. PCT/EP2006/060985, filed Mar. 23, 2006, which claims priority to German Patent Application No. DE102005013392.4, filed Mar. 23, 2005, German Patent Application No. DE102005049395.5, filed Oct. 13, 2005, and German Patent Application No. DE102006013626.8, filed Mar. 22, 2006, the contents of such applications being incorporated by reference herein.
1. Field of the Invention
The present invention relates to an electrohydraulic brake system with driving dynamics control comprising a master cylinder that is operable by means of a brake pedal and includes at least one piston, which is displaceably arranged in a housing of the master cylinder and delimits a hydraulic pressure chamber together with the housing, the pressure chamber being connectable to an unpressurized pressure fluid reservoir by way of a pressure fluid reservoir connection and a pressure fluid channel and to wheel brakes by way of an outlet, with a pressure fluid supply device supplying pressure fluid from the pressure fluid reservoir in the direction of the wheel brakes in the case of driving dynamics control.
2. Description of the Related Art
Electrohydraulic brake systems of this type equipped with driving dynamics control, such as BASR (brake intervention traction slip control system), ARP (Active Rollover Protection) or ESP (Electronic Stability Program) with the included sub-functions ABS and TCS are principally known in the art. It may be necessary in a TCS or ESP intervention, with the master cylinder non-activated or activated, to replenish pressure fluid out of the pressure fluid reservoir in the direction of the wheel brakes, what is done by means of the pressure fluid supply device, whose inlet is optionally connectable to the pressure chambers of the master cylinder or to the wheel brakes in order to supply fluid in the direction of the wheel brakes or in the direction of the master cylinder (return principle).
In a master cylinder disclosed in DE 101 20 913 A1, for example, the pressure fluid is aspirated to this end out of the pressure fluid reservoir through the pressure fluid channel, a supply chamber, transverse bores in the piston and the pressure chamber in a TCS intervention, in the non-activated condition of the master cylinder. In an ESP intervention in the activated condition of the master cylinder, the replenishment is carried out additionally by fluid overflow at an outside sealing lip of a sealing cup. In order to supply sufficient pressure fluid to the pressure fluid supply device at a quick rate in a TCS or ESP intervention, in particular when the master cylinder adopts its non-activated position, and in order to thereby minimize the reaction time of driving dynamics control, it is necessary in prior art brake systems to keep the throttling resistance of the transverse bores as low as possible. An additional objective is to minimize the lost travel of the master cylinder in order that brake pressure can be built up in the wheel brakes as quickly as possible. However, these requirement always necessitate a compromise between throttling resistance and lost travel.
In view of the above, an object of the invention is to provide an electrohydraulic brake system with driving dynamics control, which has a short reaction time of the driving dynamics control and, in addition, a short lost travel of the master cylinder.
According to the invention, this object is achieved in that a bypass channel is interposed between the pressure fluid reservoir connection and the outlet of the master cylinder, and a valve is arranged in the bypass channel, which allows pressure fluid flow from the pressure fluid reservoir through the bypass channel to the pressure fluid supply device and prevents pressure fluid flow in the opposite direction. As a result, the transverse bores designed in the piston can have a minimum possible cross-section irrespective of the reaction time of the driving dynamics control, what minimizes the lost travel of the master cylinder. Likewise, it is hence advantageous that the same master cylinder can be used for brake systems with different requirements as regards the fluid replenishment in the driving dynamics control case, hence, obviating the need for special components for a flow-optimized master cylinder.
The pressure fluid channel is preferably designed between the pressure fluid reservoir connection and an inlet of the master cylinder. According to a favorable embodiment, the pressure fluid channel and the bypass channel are integrated into a wall of the housing, and the pressure fluid reservoir connection is configured as a separate component, which can be fastened to the housing of the master cylinder.
According to another favorable embodiment, the pressure fluid channel, the bypass channel, and the pressure fluid reservoir connection are designed as a separate, one-piece component, which can be fastened to the housing of the master cylinder and can thus be provided as a pre-assembled unit.
In still another favorable embodiment of the invention, the pressure fluid channel, the bypass channel, and the pressure fluid reservoir connection are integrated in a wall of the housing. The advantage resulting therefrom is that only the assembly of the valve is required as an additional working step in the manufacture of the master cylinder.
It is considered as another shortcoming in the prior art master cylinder according to DE 101 20 913 A1 that, with a quick release of the applied brake, i.e. in a quick return movement of the piston in opposition to the actuating direction, pressure fluid flows abruptly from the pressure fluid reservoir into the pressure chamber in the moment when the transverse bores leave the area of a sealing cup, since vacuum or pressure below atmospheric pressure develops in the pressure chamber due to the return movement of the piston. The abrupt inflow of the pressure fluid into the pressure chamber can cause disturbing noise (cavitation bang). Therefore, a favorable embodiment of the invention provides for the bypass channel to open into the pressure chamber so that pressure fluid flow occurs from the pressure fluid reservoir through the bypass channel, the pressure chamber, and the outlet of the pressure fluid supply device in a driving dynamics control case. To this end, the valve must be designed in such a fashion that it opens at a defined pressure below atmospheric pressure, thus, avoiding an abrupt inflow of pressure fluid, i.e. a cavitation bang.
Ease of manufacture of the bypass channel is achieved in that the bypass channel, starting from the pressure fluid reservoir connection, extends directly to the pressure chamber. Further, no mounting space or only a small mounting space must be provided for the bypass channel and the valve.
In another advantageous embodiment, the bypass channel extends from the pressure fluid channel to the pressure chamber, and the housing includes an additional dome into which the valve is introduced. This allows mounting the valve in a simple fashion. Preferably, the bypass channel comprises a branch bore branching from the pressure fluid channel and a transverse bore, with the branch bore extending in parallel to a longitudinal axis of the master cylinder, while the transverse bore is positioned transversely to the longitudinal axis.
To prevent contaminants from entering the pressure chamber through the pressure fluid channel, according to a favorable embodiment, the pressure fluid channel has a first, large diameter in the area between the pressure fluid reservoir connection and the branching of the branch bore, and a second, small diameter in the area between the branch bore and the pressure chamber.
A combination of two mentioned embodiments of the invention provides that in a first brake circuit, the bypass channel extends from the pressure fluid reservoir connection directly to the pressure chamber, and that the bypass channel extends from the pressure fluid channel to the pressure chamber in a second brake circuit. Thus, the mentioned advantages are achieved for both brake circuits.
Preferably, the valve is configured as a spring-loaded or diaphragm-controlled non-return valve. This fact safeguards a conventional closing behavior of the master cylinder, since after a pressure fluid demand by way of the pressure fluid supply device, return of the pressure fluid to the pressure fluid reservoir is prevented at once. A disc in the valve can serve as a filter and/or restrictor.
Further details, features and advantages of the invention can be taken from the subsequent description of two embodiments making reference to the accompanying schematic drawings.
In the accompanying drawings:
A pressure sensor 79 at the brake line 73 is used to sense a pressure introduced by the driver, the brake line connecting the pressure chamber 4 to the wheel brakes 75, 76 of brake circuit I. Each brake line 73, 74 includes a serial arrangement of electromagnetic separating valves 80, 81 and each one inlet valve 82-85 and each one outlet valve 86-89 for each wheel brake 75-78. The two wheel brakes 75, 76; 77, 78 of each one brake circuit I, II are connected to a return line 90, 91, with the outlet valve 86-89 being respectively inserted into the line branches per wheel brake 75-78. Connected downstream of the outlet valves 86-89 in each return line 90, 91 is a low-pressure accumulator 92, 93 that communicates with an inlet of an electromotively driven pressure fluid supply device 94, 95, which is e.g. configured as a pump and feeds the two brake circuits I, II. There is a hydraulic connection between an outlet of each pressure fluid supply device 94, 95 and the associated brake circuit I, II by way of pressure channel 96, 97 and a branch line 98, 99, and the pressure increase in the wheel brakes 75-78 is controllable by way of the inlet valves 82-85. This renders it possible to introduce pressure into the wheel brakes 75-78 by way of the pressure fluid supply devices 94, 95 for driving stability intervention purposes or for braking operations, without the need for a central high-pressure accumulator such as in electrohydraulic brake systems.
In order to permit a change between ABS return delivery operation (supply direction in the direction of master brake cylinder 1) and TCS or ESP driving dynamics control operation (supply direction in the direction of the wheel brakes) by means of the pressure fluid supply devices 94, 95, a change-over valve 100, 101 is integrated in the suction branch line of each pressure fluid supply device 94, 95, which valve is able to establish a pressure fluid connection between the master cylinder 1 and the inlet of the pressure fluid supply devices 94, 95 when the driving dynamics control system is active.
The master cylinder 1 with a first and a second piston 2, 3 for a first and a second pressure chamber 4, 5 is operable by means of a brake pedal 41 illustrated in
The master cylinder 1 is of the so-called plunger type with stationary sealing cups 12, 13 arranged in a wall 7 of housing 6 and abutting on a piston wall 8, 9 with an inside sealing lip 10, 11 for sealing the pressure chambers 4, 5. Fluid can flow over outside sealing lips 42, 43 of the sealing cups 12, 13 in the direction of the wheel brake 75-78 if a pressure gradient is set between the pressure fluid supply reservoir 72, shown in dotted line, and wheel brakes 75-78. For the non-activated operating condition, a pressure-compensating connection is further established between the two pressure chambers 4, 5 by way of the pressure fluid reservoir 72 so that a general pressure balance exists also between the two brake circuits I, II for this non-activated operating condition.
Associated with each of the pistons 2, 3 is a resetting spring 14, 15, which is supported with one end 16, 17 on a piston bottom 18, 19, while with its other end 20, 21 it is supported indirectly or directly on the second piston 3 or on the housing 6. In the event of piston displacement in an actuating direction A, the resetting spring 14, 15, which is arranged at least partly in a bowl-shaped wall 24, 25 of the piston 2, 3, is compressed, and it is expanded for piston resetting purposes.
The master cylinder 1 is shown only in a highly schematic view, the resetting spring 14, 15 being supported on the second piston 3 or on the housing 6, respectively.
To improve the assembly, it is also feasible within the limits of the invention, as indicated in the second embodiment according to
In the non-activated condition of the master cylinder 1 as shown, the pressure chambers 4, 5 communicate with non-illustrated connecting sockets of the pressure fluid reservoir 72 by way of a pressure fluid channel 22, 23 and a supply chamber 26, 27 in the housing 6 as well as through transverse bores 28, 29 in the bowl-shaped wall 24, 25, that is arranged at a side 44, 45 of the first and the second piston 3, 4.
The first piston 2 is displaced in the actuating direction A to actuate the master cylinder 1. As this occurs, the movement of the first piston 2 is transmitted to the second piston 3 by way of the resetting spring 14. As soon as the transverse bores 28, 29 are disposed in the area of the sealing cup 12, 13, the so-called lost travel of the master cylinder 1 is covered, since pressure fluid cannot propagate from the supply chambers 26, 27 through the transverse bores 28,29 into the pressure chambers 4, 5. The connection between the pressure chambers 4, 5 and the pressure fluid reservoir 72 is interrupted, and pressure is built up in the pressure chambers 4, 5. An activated position of the master cylinder 1 is represented in
It can be necessary in a TCS or ESP control intervention to replenish pressure fluid from the pressure fluid reservoir in the direction of the wheel brakes, with the pistons 2, 3 non-activated or activated, what is preferably done by means of the pressure fluid supply device 94, 95, the inlet of which is optionally connectable to the pressure chambers 4, 5 of the master cylinder 1 or to the wheel brakes 75-78, in order to deliver fluid in the direction of the wheel brakes 75-78 or in the direction of the master cylinder 1 (return principle). To this end, the pressure fluid is replenished out of the pressure fluid reservoir 72 through a bypass channel 34, 35 in the direction of the wheel brakes 75-78 in a TCS or ESP control intervention.
As can be seen in
Consequently, the replenishment of the pressure fluid supply device 94, 95 through the bypass channel 34, 35 allows improving the reaction time of the driving dynamics control system, since the replenishment is given irrespective of the throttling resistance of the components of the master cylinder 1.
Valve 37, 38 is provided as a spring-loaded non-return valve, which can be configured as a diaphragm-type, ball valve or plug valve. However, all types of construction of a non-return valve are principally possible.
As can be seen from the illustration of the master cylinder 1 in
Most various embodiments of the master cylinder 1 are feasible within the limits of the invention. Thus, it is possible, on the one hand, to integrate the pressure fluid channel 22, 23, the bypass channel 34, 35, as well as the pressure fluid reservoir connection 30, 31 into the wall 7 of the housing 6, e.g. by way of casting it on. The result is that only the assembly of the valve 37, 38 would become necessary as an additional working step in the manufacture of the master cylinder 1. On the other hand, it is also possible to integrate only the bypass channel 34, 35 and the pressure fluid channel 22, 23 into the wall 7 of the housing 6, e.g. by casting it on, and to configure the pressure fluid reservoir connection 30, 31 as a separate component, which can be fastened at the housing 6 of the master cylinder 1. It is also feasible to provide the bypass channel 34, 35, the pressure fluid channel 22, 23, and the pressure fluid reservoir connection 30, 31 as a separate, integral component, which can be secured at the housing 6 of the master cylinder 1.
Furthermore, it is possible in all embodiments that the master cylinder 1 includes a device for detecting brake application, which comprises a magnet as a signal generator and a sensor element 36 shown in
It becomes obvious from
The master cylinder 1 exhibits a good replenishment behavior also in the activated condition, what is due to the replenishment of the pressure fluid through the bypass channel 34, 35, because the replenishment is provided irrespective of the throttling resistance of the components of the master cylinder 1. Hence, the replenishment of the pressure fluid due to overflow of the outside sealing lip 42, 43 of the sealing cup 12, 13 is omitted.
This allows reducing also the spring cushioning and, thus, the efficiency of the master cylinder 1, since it is no longer required to overcome a vacuum during replenishment, which is applied to the sealing cup 12, 13 until the outside sealing lip 42, 43 turns about.
A second embodiment of a master cylinder 1 of a brake system of the invention, in which a pressure fluid channel 60, indicated only by a line, a bypass channel 52, and the pressure fluid reservoir connection 30 are integrated in the housing 6, is illustrated in
It becomes apparent from
The bypass channel 52 and the pressure fluid channel 60 can be provided during manufacture of the housing 6, or they can be provided in the housing 6 retroactively e.g. in a metal-cutting process.
Besides, this embodiment is advantageous in that, with a quick release of the brake application, disturbing noise (cavitation bang) can be avoided. This bang develops in the event of a fast return movement of the piston 2 in opposition to the actuating direction A, when pressure fluid flows abruptly from the pressure fluid reservoir 72 into the pressure chamber 4 in the moment when the transverse bores 28 leave the area of the sealing cup 12, and when a vacuum or pressure below atmospheric pressure develops in the pressure chamber 4 due to the return movement of the piston 2. For this purpose, the valve 37 must be designed in such a manner that it opens at a defined pressure below atmospheric pressure, whereby an abrupt inflow of pressure fluid, i.e. a cavitation bang, can be prevented.
Valve 37 is provided as a spring-loaded non-return valve in this embodiment and includes a valve seat 53, a valve pin 54, a valve accommodation 55, and a valve spring 56. The attachment in the bypass channel 52 is executed by a securing element 57 fixing the valve accommodation 55 in the bypass channel 52. Furthermore, a disc 58 is arranged, against which the valve spring 56 bears and which can serve as a filter.
The bypass channel 59 and a pressure fluid channel 61 of this embodiment are shown in detail with respect to
As is obvious, the bypass channel 52 with the non-return valve 37 is provided in brake circuit I according to
A bypass channel 59 and a non-return valve 38 are provided in the second brake circuit II according to
As can be seen in addition, it is feasible on account of the bypass channels 52, 59 to simplify the design of the housing 6 and to omit the transverse bores 28, 29 of the pistons 2, 3 shown in
Principally, the bypass channels 34, 35, 52, 59 described according to the embodiments can be provided in only one brake circuit or in both brake circuits I, II. It is also possible then to position the non-return valve 37 in the first brake circuit I in an additional dome and to design the bypass channel similarly to the bypass channel 59.
As becomes apparent from
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 013 392.4 | Mar 2005 | DE | national |
| 10 2005 049 395.5 | Oct 2005 | DE | national |
| 0 2006 013.626.8 | Mar 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/060985 | 3/23/2006 | WO | 00 | 12/3/2008 |
