The invention is based on a hydraulic vehicle brake system having a service brake that can be actuated by muscle force and having a device for regulating wheel slip, in accordance with the characteristics of the preamble to claim 1.
Wheel-slip-regulated vehicle brake systems are understood hereinafter to mean anti-lock vehicle brake systems (ABS), vehicle brake systems with traction control (TC), or vehicle brake systems with an electronic stability program (ESP). Such vehicle brake systems have a hydraulic unit connected between a master cylinder, which is actuatable by the driver, and at least one wheel brake. This hydraulic unit is equipped with, among other elements, magnetically actuatable multi-way valves, pumps, a pump drive, and reservoirs that supply the pumps with pressure fluid. For actuating the pump drive, a drive motor is also present. Via an electronic control unit, the drive motor and the multi-way valves can be triggered for regulating the pressure in the wheel brakes as needed. Detailed information going beyond this can be found in the discussion in the brochure entitled “Fachwissen Kfz-Technik, Sicherheits-und Komfortsysteme, Fahrstabilisierungssysteme” [Automotive Technology, Safety and Comfort Systems and Stabilizing Systems], Gelbe Reihe [Yellow Series], 2004 Edition, Robert Bosch GmbH, Stuttgart, ISBN 3-7782-2026-8, in particular beginning on page 90.
The vehicle brake systems described therein are similar to one another in terms of the layout of their hydraulic circuit diagram, but they differ in their engineering effort and expense depending on the scope of their function. In practice, for instance, different structural forms of pumps and/or a greater or lesser number of differently designed multi-way valves are used in order to achieve whatever functionality is wanted. Anti-lock vehicle brake systems, for instance, make do with non-self-aspirating pumps, known as return pumps. The object of these pumps, in a braking event involving existing wheel slip, is to pump pressure fluid from an affected wheel brake back to the master cylinder in order to lower the brake pressure. Since because of the actuation of the master cylinder by the driver taking place at that time the pressure fluid in the wheel brake is already at elevated pressure, the pump itself need not perform any suction work.
Vehicle brake systems with a TC or ESP function, by comparison, must be capable of building up a brake pressure in one or more wheel brakes, regardless of any actuation of the master cylinder by the driver, so as to eliminate the wheel slip occurring upon acceleration of the vehicle or on cornering. This requires pumps that are designed to be self-aspirating. Self-aspirating pumps are capable of pumping pressure fluid even if there is no pressure difference or only a slight pressure difference at their inlet side. An exemplary embodiment of a self-aspirating pump is already known for instance from German Patent Application DE 199 28 913 A1.
Regardless of the type of vehicle brake system, the pumps are preceded by hydraulic reservoirs. These reservoirs make pressure fluid available to the pumps and thereby assure pump startup. Known vehicle brake systems use spring piston reservoirs for this purpose. These reservoirs include a piston, guided movably in a reservoir housing, which by circumferential sealing divides a first storage chamber, which can be filled with pressure fluid, from a second storage chamber, which is filled with a gas. The piston is urged by a spring in the direction of its basic position. In this basic position, there is no pressure fluid in the first storage chamber. In known reservoirs, the inflow and outflow of pressure fluid take place through a common supply conduit. Such reservoirs are described for instance in German Patent Application DE 199 42 293 A1.
In the event of an emptied reservoir, to prevent pressure fluid aspirated from the master cylinder by the pump from flowing to the storage chamber, a check valve is disposed in the supply line to such a reservoir. Known check valves have a valve closing body, acted upon by a spring, for controlling a valve seat.
A defective, leaky check valve, in conjunction with the sole supply conduit of the reservoir, would have the effect that the underpressure generated by the self-aspirating pump could affect the wheel brakes. Because of this underpressure, the brake pistons of these wheel brakes will be put in an extreme position. In a subsequent braking event, a disproportionately large amount of pressure fluid would therefore have to be positively displaced into the wheel brakes for the sake of building up brake pressure. The driver could perceive this from a long pedal travel, which could be irritating with regard to the capability of the vehicle brake system to function.
Furthermore, the number of different components for vehicle brake systems with a variable functional scope increases the costs for development and maintenance of a modular system. In addition, relatively many individual components have to be installed to make the known vehicle brake systems, which adversely affects production costs and the resultant structural volume. Known vehicle brake systems furthermore have the potential for improvement in terms of their functional properties when brake slip regulation occurs.
A hydraulic vehicle brake system according to the invention, as defined by the characteristics of claim 1, has the advantage over the prior art that it makes do with fewer different individual parts and is thus more economical. The individual parts used can be used both for anti-lock vehicle brake systems and for traction control or stability control programs. A vehicle brake system of the invention has improved functional properties during the regulation of the wheel slip, and because of the reduced number of individual parts, it makes more-compact dimensions of its hydraulic unit possible. These advantages are attained, among other ways, by the use of a self-aspirating pump for all the different kinds of vehicle brake systems, that is, including for purely anti-lock brake systems, in conjunction with hydraulic reservoirs that are each supplied with pressure fluid via an inlet and via an outlet separate from the inlet. The reservoirs used have a freely movable separator element, disposed between two end positions, for dividing a first storage chamber from a second storage chamber. Furthermore, this separator element is capable, in one of its end positions, of blocking off a pressure fluid-conducting connection from the inlet to the outlet of the reservoir. It functions without an additional spring element, and as a result, the volume of pressure fluid that can be stored in the storage chamber is increased, in comparison to a spring piston reservoir, while the dimensions are unchanged. Moreover, the reservoir has a pressure/volume characteristic curve with improved hysteresis, since the influence of the spring element on the hysteresis is eliminated. Further advantages or advantageous refinements of the invention will become apparent from the dependent claims and from the ensuing description.
Claim 2 seeks protection for a check valve of special embodiment disposed in the outlet of the reservoir. This check valve prevents a return flow of pressure fluid to the storage chamber of the reservoir and, because of the additional sealing function of the separator element of the reservoir, it can also be embodied without a restoring spring. Besides the savings in terms of parts costs, the check valve thus is more compact and more economical, compared to known arrangements. Such a check valve is necessary only in vehicle brake systems with an electronic stability program or traction control, since in those cases a buildup of brake pressure can occur independently of the driver, and since for this pressure buildup, pressure fluid may under some circumstances have to be aspirated from the master cylinder by the pump. In that case, the check valve prevents pressure fluid coming from the master cylinder from flowing into the reservoir. Anti-lock vehicle brake systems make do without this check valve.
With claims 3 through 7, alternative variant embodiments for a reservoir according to the invention, with a separator element that seals off in one end position, are claimed, which are equally advantageous with respect to their small installation space and their costs.
Claim 8 is based on an advantageous number and disposition of the inlets and outlets opening into the first storage chamber of such a reservoir.
The invention is shown in the drawings and described in further detail in the ensuing description. The drawings include a total of six figures, in which
Further variant embodiments for reservoirs can be found in
Finally,
To this extent, this layout of a hydraulic vehicle brake system is prior art. For the mode of operation of this vehicle brake system, reference can therefore be made to the discussion in the brochure mentioned at the outset.
The invention is distinguished over the vehicle brake system explained in this brochure by the embodiment of the reservoirs 30 provided, the connection of these reservoirs 30 to the hydraulic circuits, and the structural embodiment of the check valves 32 employed. The modified embodiment of the reservoir 30 on which the invention is based can be seen in
A cup-shaped support element 62, which can for instance be made by deep-drawing from a sheet-metal blank, is press-fitted into the fastening portion 58. The opening 64 of the support element points in the direction of the outlet 46 and is completely covered by an elastic diaphragm 66 of pressure fluid-resistant material. This diaphragm 66 is crimped along its outer circumference to the support element 62, and the circumference of the support element 62 that is created by the crimping serves simultaneously to anchor this support element 62 by nonpositive engagement in the fastening portion 58. A sealing plate 68 rests on the outside, toward the outlet 46, of the diaphragm 66. This sealing plate is joined by positive engagement to the diaphragm 66, specifically with the aid of a knob 70 protruding in the direction of the outlet 46. The knob 70 penetrates a recess in the center of the sealing plate 68 and with its thickened head engages the recess from behind. The sealing plate 68 covers the cross section of the outlet 46 completely, but it has a smaller outer diameter compared to the inner diameter of the opening 64 in the support element 62. As a result, between the inner end of the crimping and the sealing plate 68, an annular chamber 72 is created, defined in the axial direction by the diaphragm 66 and the stop shoulder 60. It must be assumed that the at least one inlet 44 (
The diaphragm 66, together with the sealing plate 68, forms a separator element that is received freely movably in the support element 62 and that seals off a (second), gas-filled storage chamber 74, disposed in the interior of the support element 62, from a (first) storage chamber 76 that can be filled with hydraulic pressure fluid of the vehicle brake system. This first storage chamber 76 is located between the sealing plate 68 and the check valve 32, the check valve being placed axially spaced apart from the sealing plate 68 in the outlet 46 of the reservoir 30. It increases its volume when pressure fluid flows in, because the sealing plate 68 lifts from the stop shoulder 60 and moves into the interior of the support element 62. To a corresponding extent, the volume of the storage chamber 74 decreases.
The aforementioned check valve 32 comprises a valve seat part 80, in the form of a perforated disk which is press-fitted into the outlet 46 until it stops against a shoulder 82. The valve seat part 80 cooperates with a valve closing body 84, here shown in the form of a ball as an example. The ball is received freely movably, downstream of the valve seat part 80, in a cylinder portion 86 of the outlet 46 and controls a conically shaped valve seat 88 on the inside of the perforated disk. A constriction 90 of the outlet 46, embodied downstream of the cylindrical portion 86, forms the connection of the check valve 32 to an intake side of the pump 26 (see
The view in
The roll diaphragm 100 is likewise received freely movably between two end positions. In the first end position, shown, the pressure fluid-filled first storage chamber 76 has been emptied completely. The roll diaphragm 100 now rests with its control cross section 106 on the side of the valve seat part 80 diametrically opposite the valve seat 88 of the check valve 32. Thus the roll diaphragm 100 seals off the inflow cross section of the check valve 32 and blocks any communication from the inlet 44 of the reservoir 30 to the outlet 46. The inlet 44 cannot be seen in
In the exemplary embodiment of
As a result of the screwing-in torque of the closure stopper 94, the diaphragm 66 is fixed between the hollow cylinder and the stop shoulder 60 of the bore 50. The inlet 44 and the outlet 46 of this reservoir 30 extend parallel to one another in the screw-in stub of the reservoir housing 31. The result at its orifice into the bore 50 is a rib 116, which cooperates with the diaphragm 66. The view in
In this exemplary embodiment, the rigid piston 120 acts as a separator element between two storage chambers 74 and 76. The first storage chamber 76, which can be filled with the hydraulic pressure fluid of the vehicle brake system, is embodied between the piston bottom 122 and the check valve 32; the second, gas-filled storage chamber 74 is defined by the interior of the piston 120 and by the closure cap 128. In the position shown, the first storage chamber 76 has essentially been emptied of hydraulic pressure fluid, and as a result, the piston 120 with the protrusion 124 from its piston bottom 122 seals off the inflow cross section of the check valve 32. Since in this exemplary embodiment as well it must be assumed that the inlet 44, not shown, discharges into the first storage chamber 76, the piston 120 in the end position shown thus also blocks off the pressure fluid-conducting connection from the inlet 44 to the outlet 46.
For bleeding the vehicle brake system 10 in
It is understood that refinements or additions to the exemplary embodiments described can be made without departing from the fundamental concept of the invention.
Number | Date | Country | Kind |
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10 2006 026 155.0 | Jun 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP07/54051 | 4/25/2007 | WO | 00 | 12/8/2008 |