Pressure medium storage device with reservoir function

Abstract

The known functions of a pressure medium storage device are extended to the extent that the reservoir provides a supply of a pressure medium with low pressure loss for the suction pumping device within the brake assembly. [Solution] The pressure medium storage device (10) includes a hollow storage housing (12) in which a separation element (14) is housed so as to be longitudinally slidable in both spatial directions. The separation element (14) separates a first housing chamber (16a) from a second housing chamber (16b) and is operated toward its base position by an elastic return device (20). According to the present invention, a pressure medium storage device (10) is proposed such that the first housing chamber (16a) has a chamber volume V0 greater than zero at the base position of the separation element (14) and is filled with a hydraulic pressure medium.

Description

Technical Field

[0001] Disclosure of the Invention Background Art The present invention relates to a pressure medium reservoir device for accommodating a pressure medium, particularly in an electronically pressure-controllable brake system of a motor vehicle, having the features described in the generic concept of claim 1.

[0002] Electronically pressure-controllable brake systems in motor vehicles are well known. Electronically pressure-controllable brake systems in motor vehicles are used to control the brake pressure for each individual wheel depending on the slip behavior currently present at the corresponding wheel. For this purpose, they are equipped with a hydraulic assembly, which includes a pumping device drivable by an electric motor, an electrically controllable valve, the pressure medium reservoir device on which the present invention is based, and an electronic control device for electrically controlling the controllable components. The objectives are to prevent wheel lock and the associated unstable driving state of the motor vehicle and to maintain the steering ability of the motor vehicle during the braking process on a slippery road surface. Such hydraulic brake systems are also variously known under the names ABS system, ESP brake system, or anti-lock brake system.

[0003] To prevent impending wheel slip, in such a brake system, the brake pressure of the wheel at risk of lock is reduced by discharging the pressure medium from the corresponding wheel brake via the wheel outlet valve. For this purpose, this wheel outlet valve is electrically controlled by an electronic control device and switched from its initial closed position to a flow-through position.

[0004] The pressure medium storage device that forms the basis of the present invention is used to contain the pressure medium discharged from the wheel brake. The pressure medium storage device that forms the basis of the present invention includes a separation element, to which a force is applied in the direction of the base position by an elastic return device. The separation element separates the interior of the storage housing into a first housing chamber and a second housing chamber separated from the first housing chamber, at least one of the housing chambers being hydraulically in contact with the brake circuit of the brake system, which has a pressure feeder, via a pressure medium connection. In the base position of the separation element, this housing chamber is empty.

[0005] Since the volume of the housing chamber containing the pressure medium is structurally limited, controlling the brake pressure requires either controlling the emptying of the housing chamber or understanding its fill level. The fill level of the housing chamber is typically calculated using a balancing algorithm, which compares the volume of incoming pressure medium to the structurally defined total volume of the housing chamber. However, the accuracy of this algorithm is only sufficient if all parameters, such as system density, spring stiffness of the return mechanism, component dimensions, and pressure medium temperature, correspond to their rated values. Since the pressure medium temperature rarely matches in practice, this algorithm is merely an estimation model, and its accuracy is not always sufficient for optimal brake pressure control. To address this issue, the housing chamber is intentionally emptied as frequently as possible.

[0006] When emptying in this manner, an elastically biased separation element pushes the pressure medium contained within the housing chamber back into the brake system's pressure medium reservoir via a valve switched to the flow position by an electronically controlled device, or the pressure medium is pumped back from the housing chamber into the brake circuit by a pumping device driven by an electric motor. The disadvantage in this case is that the components are operated more frequently, and consequently, the demands on the lifespan of the components increase.

[0007] In braking systems, the pressure loss that occurs during flow through the braking system is critical to the achievable braking output. Pressure loss downstream of the pumping unit is technically easily controllable in this regard because it can be compensated for by increasing the power consumption of the pumping unit's drive mechanism. In contrast, pressure loss upstream of the pumping unit, i.e., on the suction side of the pumping unit, can result in limited pumping behavior until the pumped flow completely stops. Therefore, in the case of conventional braking systems, the existing deceleration performance cannot always be fully utilized depending on the situation. For example, while technical solutions in the form of suction lines with low pressure loss are known, they are costly, require structural space, and are therefore only partially suitable for mass production.

[0008] Advantages of the invention The present invention extends the known functions of a pressure medium storage device by the extent that it provides a reservoir that supplies a pressure medium with low pressure loss for a suction pumping device within a brake assembly. Unlike the prior art, where only pressure medium storage devices are known that have a response pressure greater than zero when empty and therefore can only store the pressure medium under the corresponding positive pressure in this state, the pressure medium storage device according to the present invention can store the pressure medium under atmospheric pressure. No sealing components, such as valves, are required to hold the pressure medium in the housing chamber under positive pressure or to prevent the housing chamber from spontaneously emptying when the vehicle is stationary. The present invention enables an increase in the pumping output of the pumping device because the pressure loss on the suction side can be kept very small, and furthermore, the pressure loss on the suction side does not depend on customer-specific boundary conditions such as the length and / or diameter of the suction line, the structure of the master brake cylinder, and / or the type of brake fluid used.

[0009] According to the present invention, the brake output of the brake system is no longer limited by the pumping output of its hydraulic assembly, but rather depends solely on the limits imposed by the vehicle's driving dynamics. The latter cannot be fully achieved with known pressure medium storage devices.

[0010] Furthermore, an advantage of the present invention is that it can be realized by measures to structurally adapt it to existing components of any pressure medium storage device, that is, without requiring additional components, and therefore without significantly increasing the need for parts, mounting, structural space, or cost of the pressure medium storage device. Moreover, the present invention does not adversely affect the flow characteristics of the hydraulic assembly.

[0011] Further advantages or advantageous forms of the present invention will become apparent from the dependent claims and / or the following description.

[0012] According to the present invention, a filling level equilibration algorithm for estimating the volume of pressure medium present in the reservoir chamber is omitted, particularly after a relatively long period of inactivity of the brake system. This makes it possible to achieve braking functions that were impossible with conventional brake systems equipped with pressure medium reservoir devices, which rely on suction from an external reservoir with significant pressure loss. This includes, for example, emergency braking functions when temperatures are low and the pressure medium is correspondingly viscous, or redundant functions for pressure medium supply in brake systems that do not require a hydromechanical fallback level.

[0013] The present invention is preferably applicable in automotive brake systems, but alternatively, it may also be used in hydraulic assemblies for non-automotive engineering applications, particularly when large pressure build dynamics are important.

[0014] The dependent claims describe particularly preferred means for constituting, arranging and mounting, and / or structurally realizing an elastic return device for a separation element.

[0015] drawing Several embodiments of the present invention are shown in the drawings and will be described in detail below.

[0016] For this reason, the drawings include multiple diagrams in which, for simplification, corresponding components or groups of components are denoted by the same reference numeral. [Brief explanation of the drawing]

[0017] [Figure 1] These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 2] These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 3]These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 4] These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 5] These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 6] These figures show a simplified schematic representation of one embodiment of the pressure medium storage device that forms the basis of the present invention, based on a longitudinal cross-section. [Figure 7a] These figures disclose further embodiments of the present invention in different operating states. [Figure 7b] These figures disclose further embodiments of the present invention in different operating states. [Figure 7c] These figures disclose further embodiments of the present invention in different operating states. [Figure 7d] These figures disclose further embodiments of the present invention in different operating states. [Figure 8] This figure shows details of one embodiment relating to the axially immovable locking of the return device to the separation element and one end face of the storage housing.

[0018] Description of the Examples A first embodiment of the pressure medium storage device (10), as shown in Figure 1, has a hollow cylindrical storage housing (12) with both ends closed, and a separation element (14) is housed inside the storage housing (12) so as to be longitudinally slidable in both spatial directions. The separation element (14) is exemplary in the form of a cylindrical piston, but may also be configured as an elastic diaphragm or deformable bellows made of plastic or metal, having a circumferential section attached to the inner wall of the storage housing and a central bottom region movable relative to this section.

[0019] The separating element (14) or the illustrated piston is sealed on the circumferential side with respect to the inner wall of the reservoir housing (12), thereby dividing the internal space into a first housing chamber (16a) and a second housing chamber (16b) separated from this first housing chamber (16a). The first housing chamber (16a) can be brought into contact with the hydraulic brake circuit of a brake system (not shown) so as to conduct a pressure medium via a plurality of exemplary fluid connections (18), while a return device (20) for applying a force to the separating element (14) is arranged in the second housing chamber (16b). The return device (20) is configured as a cylindrical spring or a coil spring, and a first end of this cylindrical spring or coil spring is axially immovably locked to the rear surface of the separating element (14) that is not subjected to a force by the hydraulic pressure medium, and a second end opposite to the first end is similarly axially immovably fixed to the opposite end face of the reservoir housing (12). Based on the return device (20) being attached to the separating element (14) on the one hand and to the reservoir housing (12) on the other hand, it can affect the separating element (14) by a compressive force or by a tensile force having a direction opposite to the compressive force.

[0020] The return device (20) is illustratively shown as a conventional cylindrical spring with a spring winding having a constant slope. However, this form is not necessarily essential for the present invention. Alternatively, it is also possible to use a cylindrical spring, a disc spring, a spiral spring, a conical spring, a bending beam, an elastomer body, a pneumatic spring element, or a combination of a pneumatic spring element and one or other mechanical spring elements, having a spring winding with a varying slope and / or outer dimensions, and this enumeration is not intended to be exhaustive. To realize a pneumatic spring, the second housing chamber (16b) can be filled with a compressible gas based on the gas connection (22) suggested by the dashed line. Furthermore, it is possible to adapt and set the filling pressure, and thus the spring characteristics of the pneumatic spring element, via this gas connection (22) as required.

[0021] In the illustrated basic position of the pressure medium reservoir device (10), the separating element (14) has no effective longitudinal force in the hollow interior of the reservoir housing (12) and is in a state of force equilibrium. In the case of the illustrated embodiment, this means that the longitudinal force induced on the separating element (14) by the pressure in the first housing chamber (16a) cancels out the second longitudinal force acting in the opposite direction and applied to the separating element by the pressure in the second housing chamber (16b).

[0022] According to the present invention, in this basic position of the separating element (14), the first housing chamber (16a) has a chamber volume V0 different from zero filled with the hydraulic pressure medium of the brake system. The first housing chamber (16a) is in contact with the brake circuit via at least one of its fluid connections (18) and, within the brake circuit, is in contact particularly with the suction side of a pumping device drivable by the aforementioned electric motor.

[0023] The fluid connection (18) allows the volume of the first housing chamber (16a) to be expanded relative to the chamber volume V0 at its base position using hydraulic positive pressure, or reduced accordingly using hydraulic negative pressure. The separation element (14) in this case reciprocates within the reservoir housing (12), thereby changing the volume of the housing chambers (16a, 16b) in the opposite direction. The extent to which a pressure change results in a volume change may be determined by the structural design of the stiffness of one or more springs forming the return device (20). Since the pressure medium reservoir device (10) is located within the brake circuit near the pressurizer of the brake system, structurally matching the stiffness of the spring elements of the return device (20), together, enables particularly low-loss fluid supply from this pressurizer.

[0024] Figure 2 shows a second embodiment of the present invention, which differs from the embodiment shown in Figure 1 in terms of the structure of the return device (20) of the present invention. The return device (20) shown in Figure 2 consists of a plurality of mechanical spring elements (24a, 24b) arranged in series with respect to each other and connected to each other as an integrated spring configuration. Two spring elements (24a, 24b) are disclosed merely illustratively, and these two spring elements (24a, 24b) are arranged together in a second housing chamber (16), and the spring stiffness of each of these two spring elements (24a, 24b) is different from that of the other. In this case, the first spring element (24a) facing the separation element (14) has higher spring stiffness than the second spring element (24b) of the return device (20) which is located on the opposite side of the separation element (14). Therefore, when a compressive or tensile load is applied to the separation element (14), the first spring element (24a) deforms only after the second spring element (24b) has already deformed to its maximum extent. Both spring elements (24a and 24b) are here exemplary as cylindrical springs.

[0025] Similar to the embodiment shown in Figure 1, in the second embodiment, one end of the return device (20) is firmly attached to the separation element (14), and the other end is firmly attached to one end face of the storage housing (12). Thus, this return device (20) is also suitable for applying tensile or compressive force to the separation element (14), or constitutes a tension-compression-spring configuration. Figure 2 again shows the separation element (14) in its basic position, in which the separation element (14) is positioned inside the storage housing (12) without longitudinal force. The first housing chamber (16a) has a non-zero chamber volume V0 filled with a pressure medium, but this chamber volume V0 is dimensionally smaller in this embodiment than in the embodiment shown in Figure 1.

[0026] The embodiment shown in Figure 3 differs from the embodiment shown in Figure 2 in that the return device (20) consists of a combination of spring elements (24a, 24b) of different structural types, namely a combination of cylindrical springs arranged in series with a conical spring. In this case, the conical spring faces the separation element (14), and the cylindrical spring is positioned on the opposite side of the separation element (14). Both spring elements (24a, 24b) are again housed together in the second housing chamber (16b), and are firmly connected to each other at their opposing ends to form a single spring configuration. One free end of this spring configuration is attached to the separation element (14), and the other free end is attached to one of the end faces of the storage housing (12). Unlike the illustration in Figure 3, the spring configuration may alternatively be positioned in the first housing chamber (16a). In this embodiment as well, the return device (20) forms a tension-compression-spring configuration, which can, depending on the circumstances, apply a tensile force or a compressive force to the separation element (14).

[0027] The embodiment shown in Figure 4 also uses a return device (20) composed of multiple spring elements (24a, 24b), but in the embodiment shown in Figure 4, unlike the modified example described above, each individual spring element (24a or 24b) is individually located within one of the two housing chambers (16a, 16b). Exemplarily, the two spring elements (24a, 24b) are identical to each other in terms of form and dimensions and affect the corresponding separation element (14) on opposite sides. In this embodiment, it is possible to omit attaching the spring elements (24a, 24b) to the separation element (14) or the storage housing (12). This is because, depending on the direction of displacement of the separation element (14), one or the other spring element (24a, 24b) acts as a compression spring that loads the separation element (14). Therefore, the tensile force generated by the spring elements (24a, 24b) does not apply force to the separation element (14) in this embodiment.

[0028] Figure 4 also shows the pressure medium storage device (10) in its basic position, in which the separation element (14) separates the inside of the storage housing (12) into two housing chambers (16a, 16b) of the same size, each having a chamber volume that is not equal to zero, based on the fact that their respective spring forces are equal.

[0029] Figure 5 shows a further embodiment comprising spring elements (24a, 24b) housed in different housing chambers (16a, 16b). However, in the fifth embodiment, these spring elements (24a, 24b) have different configurations. The spring element (24a) in the first housing chamber (16a), which is filled with a pressure medium, is configured as a conical spring, while the spring element (24b) in the second housing chamber (16b) is configured as a conventional cylindrical spring.

[0030] In the embodiment shown in Figure 6, a hollow cylindrical bellows is inserted as a spring element (24a) in the first housing chamber (16a) instead of the cylindrical spring shown in Figure 5, and this bellows may be selectively made of elastomer or metal. One end of the bellows is closed by a separation element (14), and the other end is closed by a storage housing (12), while a fluid connection (18) provided on the other side opens into the hollow interior of the spring element (24a) or the bellows, and the first housing chamber (16a), which can be filled with a pressure medium, has a chamber volume V0 that is not equal to zero. A second spring element (24b) acting on the separation element (14) is housed in the second housing chamber (16b) and is configured as a cylindrical spring. The compressive force of the second spring element (24b) acts against the spring force of the bellows.

[0031] Figures 7a to 7d show further embodiments of the pressure medium storage device (10) according to the present invention under different operating conditions.

[0032] Figure 7a shows the pressure medium storage device (10) in its basic position, in which the return device (20) is relaxed, and therefore the separation element (14) is positioned within the storage housing (12) without any effective longitudinal force. The first housing chamber (16a), according to the present invention, has a chamber volume V0 that is not equal to zero and is filled with a hydraulic pressure medium under atmospheric pressure. The return device (20) is located within the second housing chamber (16b) and, in this embodiment, is configured as a tension-compression-spring assembly, with one end of the tension-compression-spring assembly firmly attached to the separation element (14) and the other free end firmly attached to the end face of the storage housing (12). The tension-pressure-spring configuration is subdivided into spring elements (24a, 24b) on the separation element side and spring elements (24a, 24b) on the separation element side, and these spring elements (24a, 24b) differ from each other in terms of the inclination of their respective spring windings. The inclination of the spring winding in the first spring element (24a) on the separation element side is set to be greater than the inclination of the spring winding in the second spring element (24b) on the separation element side, and therefore, the spring element (24a) on the separation element side deforms first when a pressure load is applied to the separation element (14).

[0033] In Figure 7b, the separation element (14) is loaded by a negative pressure within the first housing chamber (16a). This negative pressure is generated by a pumping device driven by an electric motor in the brake circuit and transmitted into the first housing chamber (16a) via one of several fluid connections (18). In the first housing chamber (16a), the negative pressure loads the separation element (14) by tensile force, causing the separation element (14) to displace to the left in Figure 7b against the force of the return device (20). Accordingly, the volume of the first housing chamber (16a) decreases, while the return device (20), based on its attachment to the separation element (14) and the reservoir housing (12), takes a correspondingly longer time to eventually balance the spring force against the compressive force.

[0034] In contrast, Figure 7c shows the pressure medium reservoir device (10) in operation, where a compressive force is applied to the separation element (14) by the pressure medium in the first housing chamber (16a). Such a compressive force is generated when the pressure medium from the wheel brake is released into the first housing chamber (16a), for example, when the brake pressure needs to be reduced because wheel slip is imminent. Based on the effective pressure load, the separation element (14) moves to the right in Figure 7c against the force of the return device (20), the volume of the first housing chamber (16a) increases relative to its base position, and the volume of the second housing chamber (16b) decreases accordingly. Thus, the return device (20), located in the second housing chamber (16b), is compressed in the separation element (14) until a force balance is achieved between the compressive force and the spring force of the return device (20). In Figure 7c, this spring force can be applied only by the spring element (24a) on the separation element side of the return device (20), and therefore, the spring element (24b) that is away from the separation element of the return device (20) does not deform.

[0035] The latter spring element (24b) changes in the operating state shown in Figure 7d. In the operating state shown in Figure 7d, the pressure in the first housing chamber (16a) increases to the maximum pressure, and therefore, an effective compressive force on the separation element (14) presses the return device (20) against the block. In this operating state, the separation element (14) is displaced to its maximum extent, and the first housing chamber (16a) of the pressure medium storage device (10) has its maximum chamber volume.

[0036] Finally, Figure 8 further illustrates one embodiment of a technical implementation for attaching the return device (20) to the separation element (14) on one side and to the end face of the storage housing (12) on the other side.

[0037] The return device (20) is also realized as a tension-compression-spring configuration in the embodiment shown in Figure 8, and has a first spring element (24a) on the separation element side in the form of a conventional cylindrical spring with a spring winding of a certain inclination, and a second spring element (24b) formed at one end of this cylindrical spring without a transition section. The second spring element (24b) is in the form of a flat spiral spring wound inward, and has a pin (26) formed in the center that protrudes outward in the axial direction in the direction of the longitudinal axis of the return device (20).

[0038] The pin (26) of the return device (20) is inserted into the corresponding housing opening (28) provided on the end face of the storage housing (12) until the second spring element (24b) of the return device (20) abuts substantially coplanar with the end face, and the pin (26) protrudes axially from the housing opening (28) of the storage housing (12). Plastic deformation of the material of the storage housing (12) around the housing opening creates a frictional coupling between the storage housing (12) and the pin (26), which connects both components axially immovably to each other.

[0039] The opposite end of the return device (20) has a polished winding end (30) that abuts the subsequent spring winding axially and circumferentially, and this winding end (30), together with the first complete spring winding, constitutes a flat annular end (32) of the return element (20).

[0040] To attach the annular end (32) of the return element (20) to the separation element (14) or piston, the separation element (14) is configured as a hollow piston, into which the first spring element (24a) of the return device (20) partially protrudes. A circumferential collar projecting inward is formed at the end of the inner circumference of the hollow piston that faces the bottom of the piston, and an annular housing groove (34) is formed in this circumferential collar. The axial and radial dimensions of the annular housing groove (34) are set to be slightly smaller than the corresponding outer dimensions of the annular end (32) of the return device (20). Contrary to the illustration in the drawing, the housing groove (34) may be formed interrupted in the circumferential direction.

[0041] By press-fitting this annular end (32) of the return device (20) into the housing groove (34) of the separation element (14) by shape coupling, a shape coupling is formed between the two components, and based on this shape coupling, the return device (20) can now transmit tensile or compressive force to the separation element (14).

[0042] Of course, in the embodiments described above, there may be modifications and / or advantageous developments that do not deviate from the scope of protection defined by one of the independent claims.

Claims

1. In particular, a pressure medium storage device (10) that houses a pressure medium within an electronically pressure-controllable brake system of an automobile, wherein the pressure medium storage device (10) Storage housing (12) and A separation element (14) is housed longitudinally movably within the storage housing (12), wherein the separation element (14) separates the first housing chamber (16a) of the storage housing (12) from the second housing chamber (16b), and at least the first housing chamber (16a) has a fluid connection portion (18) for hydraulically contacting the first housing chamber (16a) with the brake system, An elastic return device (20) that operates the separation element (14) in the direction of the basic position and A pressure medium storage device (10) comprising: The first housing chamber (16a) has a chamber volume V greater than zero, filled with a hydraulic pressure medium at the basic position of the separation element (14). ０ has A pressure medium storage device (10) characterized by the above.

2. The separation element (14) is configured as a piston, diaphragm, bellows, or elastomer. The pressure medium storage device according to claim 1.

3. The return device (20) has a plurality of elastic spring elements (24a, 24b), The plurality of elastic spring elements (24a, 24b) are arranged together in the first housing chamber (16a), or are arranged separately in each of the housing chambers (16a, 16b). A pressure medium storage device according to claim 1 or 2.

4. The separation element (14) can be subjected to tensile or compressive force by the return device (20). When the separation element (14) is in the basic position, the effective tensile force is in equilibrium with the effective compressive force. A pressure medium storage device according to any one of claims 1 to 3.

5. Each of the spring elements (24a, 24b) is configured as a cylindrical spring, spiral spring, conical spring, disc spring, bellows, or bent beam, or is formed as an air spring element. A pressure medium storage device according to any one of claims 1 to 4.

6. The spring elements (24a, 24b) are positioned between the separation element (14) and the storage housing (12), and are in loose contact with the separation element (14) and / or the storage housing (12). A pressure medium storage device according to any one of claims 1 to 5.

7. Multiple spring elements (24a, 24b) are firmly connected to each other to form a single spring structure. A pressure medium storage device according to any one of claims 1 to 6.

8. One end of the return device (20) is firmly connected to the separation element (14), and the other end is firmly connected to the storage housing (12). A pressure medium storage device according to any one of claims 1 to 7.

9. The return device (20) is attached to the separation element (14) via a shape coupling, The shape coupling is formed, in particular, by elastically pressing the flat annular end (32) of the return device (20) into a corresponding receiving groove (34) provided in the separation element (14). A pressure medium storage device according to any one of claims 1 to 8.

10. One end of the return device (20) is fixed to the storage housing (12) in an axially immovable manner by friction coupling. The return device (20) has a pin (26), The pin (26) protrudes into a corresponding storage opening (28) provided in the storage housing (12) and is attached to the storage housing (12) by plastic deformation of the material of the storage housing (12) surrounding the storage opening (28). A pressure medium storage device according to any one of claims 1 to 9.

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