Electronically slip-controllable braking mechanism for automobiles, and method for controlling an electronically slip-controllable braking mechanism.

Abstract

This relates to an electronically slip-controllable braking mechanism. [Solution] The brake pressure modulator (18) includes a second brake pressure generator (18e) which is drivable by a drive engine (18f) and connected to the brake circuit (10) in parallel with the first brake pressure generator (12); an electrically controllable first directional control valve (18a) for controlling the pressure medium flowing into the wheel brake (16); and a pressure medium reservoir (18c) for accommodating the pressure medium that has flowed out of the wheel brake (16) within the framework of brake pressure control. An electronic control device (28) provides control according to the demands of the components. The first pressure medium connection (22) from the first brake pressure generator (12) to the second brake pressure generator (18e) is controlled by an electrically controllable second directional control valve (20).

Description

Technical Field

[0001] Background Art The present invention relates to an electronically slip-controllable brake mechanism for a motor vehicle having the features described in the superordinate concept of claim 1, and to a method for controlling an electronically slip-controllable brake mechanism having the features described in the superordinate concept of independent parallel claim 6.

Background Art

[0002] Electronically slip-controllable brake mechanisms for motor vehicles are counted in various different stages of technical expansion over the prior art, and are well-known both as vehicle brake mechanisms with an anti-lock brake function (ABS brake mechanisms) and as vehicle brake mechanisms with a driving stability control function (ESP brake mechanisms). The task of such vehicle brake mechanisms is to avoid locking of the wheels of a motor vehicle during braking and / or during driving operations, thereby maintaining the steerability of the motor vehicle or counteracting an unstable driving state.

[0003] In this case, it is assumed that the brake pressure predominantly present in the wheel brakes is adjusted according to the actual slip conditions present in the wheel associated with one of the wheel brakes. For this purpose, the electronically slip-controllable braking mechanism of an automobile is equipped with a hydraulic assembly to which the wheel brakes are hydraulically connected, and the hydraulic assembly has a device for modulating the brake pressure in the wheel brakes. This brake pressure modulator includes, in particular, a (second) brake pressure generator that can be driven by an electric motor, an electrically controllable directional control valve, a reservoir device, and a pressure medium connection that hydraulically connects these devices to each other. The electronic control unit of the hydraulic assembly electrically controls the above-mentioned devices according to the current braking desire. This braking desire may be set mechanically by the driver by operating a braking desire detection device in the form of a pedal or lever that can apply force to the first brake pressure generator or master brake cylinder, or it may be set electrically by vehicle electronics that monitor the driving conditions. The first brake pressure generator is supplied hydraulically from a reservoir that stores a hydraulic pressure medium under atmospheric pressure.

[0004] In known hydraulic units, the pressure in the brake circuit is regulated using a pressure control valve. The pressure control valve is located in a so-called second pressure medium connection, which connects a second brake pressure generator to a master brake cylinder or a first brake pressure generator. In the prior art, this pressure control valve is configured as a directional control valve that is closed when there is no current, and which can be moved from an off position to a flow position by electrical control for pressure control by an electronic control device. Furthermore, a bypass to this pressure control valve is provided, and a check valve is located in this bypass. This check valve releases the pressure medium connection from the master brake cylinder or the first brake pressure generator to the second brake pressure generator in order to allow a brake pressure higher than the predominantly present brake pressure in the brake circuit, provided by the first brake pressure generator, to reach the wheel brakes. When brake pressure is generated by a second brake pressure generator that is in parallel with the first brake pressure generator and in contact with the brake circuit, the check valve is driven to close by the predominantly present brake pressure in the brake circuit, thereby shutting off the second pressure medium connection mentioned above.

[0005] In a conventional brake system known from the prior art, when the system is in an initial or basic position where no current is applied, the first brake pressure generator is hydraulically disconnected from the brake circuit. For this purpose, a so-called second directional control valve is provided in the first pressure medium connection of the brake circuit leading from the first brake pressure generator to the second brake pressure generator. In the prior art, this second directional control valve is closed when there is no current, and is opened by an electronic control device only when the second brake pressure generator is to generate brake pressure, and for this purpose, the pressure medium from the reservoir of the first brake pressure generator is to be supplied to the second brake pressure generator. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102006026872 [Patent Document 2] German Patent Application Publication No. 102008002244 Specification [Overview of the project] [Problems that the invention aims to solve]

[0007] Disclosure of the invention However, a drawback of the normally closed second directional control valve is that it cannot spontaneously empty the pressure medium reservoir of the brake pressure modulator, which is further present in the brake circuit, connected downstream of the aforementioned second directional control valve, and equipped with a separation element biased by an elastic return element, in the direction of the first brake pressure generator. Therefore, emptying such a pressure medium reservoir presupposes electrically controlling the second directional control valve to the flow position, which causes perceptible valve noise, increases the energy demand of the brake system, and consequently has an adverse effect on the energy efficiency of the brake system. Furthermore, the demands on the lifespan of the second directional control valve increase due to the increase in the number of operating cycles that occur.

[0008] From German Patent Application Publication No. 102006026872, an electronically slip-controllable brake mechanism for an automobile is known, having the features described in the broader concept of claim 1.

[0009] In the prior art, the second directional control valve or high-pressure switching valve for controlling the first pressure medium connection from the first pressure generator to the second pressure generator is configured as a normally closed directional control valve, as described above. Therefore, in the unpowered state of the brake mechanism, this prevents the pressure medium reservoir connected downstream of the second directional control valve to the first pressure medium connection or brake circuit from spontaneously becoming empty.

[0010] In known braking mechanisms, a brake pressure set by the driver through the operation of the master brake cylinder or first brake pressure generator can reach an operating state where the brake pressure should be increased by a brake pressure modulator. Therefore, a valve that is technically capable of opening against this brake pressure set by the driver must be used as the second directional control valve. The opening force required for this necessitates a valve actuator that is reasonably powerful and requires structural space. Nevertheless, in order to use an actuator that is as compact as possible, the second directional control valve in the prior art is configured as a multi-stage valve with two control stages, each of which is associated with one valve closing element. However, such a valve structure is complex and expensive. Furthermore, the multiple control stages in the directional control valve increase the pressure loss coefficient of the directional control valve, resulting in a deterioration of the pressure build dynamics in the corresponding brake circuit. When an electric motor-assisted brake pressure generator is used as the first brake pressure generator, the energy efficiency of the brake system is further reduced due to the increased drive output of this brake pressure generator, caused by the multi-stage directional control valve.

[0011] To allow the reservoir device to be voluntarily emptied, known brake mechanisms have a separate relief channel that directly connects the pressure medium reservoir to a first brake pressure generator or master brake cylinder. This relief channel is controlled by a spring-driven check valve that opens when the pressure in the pressure medium reservoir exceeds the brake pressure provided by the first brake pressure generator. However, the drawbacks of this solution are the structural space required in the hydraulic assembly to accommodate the relief channel, the manufacturing cost of the relief channel, the additionally required check valve, and the assembly cost.

[0012] A further braking mechanism having the features described in the broader concept of claim 1, comprising a second directional control valve or high-pressure switching valve that is closed in a current-free state for controlling a first pressure medium connection, is disclosed in German Patent Application Publication No. 102008002244. In this known solution, a pressure medium connection, which is connected via a directional control valve of a brake pressure modulator, is used to empty the pressure medium reservoir. However, this solution also relies on electrical control to open one of these directional control valves, which similarly degrades the energy efficiency of the braking mechanism or imposes stricter requirements on the lifespan of the directional control valve to be controlled. [Means for solving the problem]

[0013] Advantages of the invention An electronically slip-controllable brake mechanism for an automobile, according to the features of claim 1, comprises a second directional control valve or high-pressure switching valve configured as a valve that is open in a current-free state for controlling a first pressure medium connection from a first brake pressure generator or master brake cylinder to a second brake pressure generator.

[0014] Based on such a directional control valve, the pressure medium reservoir, in contact with the first pressure medium connection, is consistently connected to the first brake pressure generator in the initial state when the directional control valve is not energized, and can spontaneously empty the pressure medium reservoir, i.e., driven by the mechanical return mechanism of the pressure medium reservoir, toward the first brake pressure generator or toward the reservoir coupled to the first brake pressure generator. Electrical control of the directional control valve or operation of the second brake pressure generator is not required to empty the pressure medium reservoir in this manner, which on the one hand shortens the operating period of these components or extends their lifespan, and on the other hand reduces the external energy consumption of the brake system. The calculation model stored in the electronic control unit for estimating the reservoir's fill level is more reliable in a brake system with a second directional control valve that is open in a no-current state, which again means shortening the operating time of the electrically operated components described above, and as a result reducing the demand for external energy. Furthermore, the braking system's switching or operating noise, which may be perceptible in some cases, is reduced, and the driver receives better tactile feedback from the braking system when applying force to the control device.

[0015] Further advantages or favorable developments will become apparent from the dependent claims and / or the following description.

[0016] If a third directional control valve, similar to the second directional control valve and also open in a current-free state, is used to control the second pressure medium connection from the second brake pressure generator to the first brake pressure generator or master brake cylinder, then a conventionally known bypass for this third directional control valve, and consequently a similarly known check valve for controlling this bypass, can be omitted without substitution. Ultimately, this reduces further structural space, additional components, and further assembly effort.

[0017] By omitting the check valve, and further omitting potential internal leakage points of the braking system, this is particularly important in the case of pressure holding operations such as, for example, the function of stopping a braked vehicle on a slope. This also omits the operating time of the brake pressure generator to compensate for possible leaks that may occur. As a result, the life cycle of the brake pressure generator is extended, the demand for external energy of the braking system is improved, and the operating noise is reduced.

[0018] Drawings Embodiments of the present invention are shown in the drawings and will be described in more detail in the following description.

Brief Description of the Drawings

[0019] [Figure 1] This is a diagram specifically showing the present invention based on a hydraulic circuit diagram.

Modes for Carrying Out the Invention

[0020] [[ID=​​​​​​​​​​To set the desired braking by the driver, the brake circuit (10) of the brake mechanism illustrated in the drawing has a master brake cylinder (12a) that can be operated by muscle power via an operating element (14) in the form of a pedal or lever. Depending on the operation, the master brake cylinder (12a) generates a brake pressure in the connected brake circuit (10). Thus, the master brake cylinder (12a) is also referred to hereinafter as the first brake pressure generator (12).

[0023] The brake circuit (10) is in contact with a pressure-operable wheel brake (16) via a brake pressure modulator (18) connected upstream thereof. The latter brake pressure modulator (18) includes, in particular, an electronically controllable first direction control valve (18a) or inlet valve, and the first direction control valve (18a) or inlet valve can regulate the inflow of the pressure medium to the wheel brake (16) and thus the build-up of the brake pressure in this wheel brake (16). Furthermore, an electronically controllable outlet valve (18b) connected in parallel to the first direction control valve (18a) is provided, and via this outlet valve (18b), the pressure medium from the wheel brake (16) can be controllably discharged in the direction of the pressure medium reservoir (18c) of the brake pressure modulator (18) for reducing the brake pressure.

[0024] The pressure medium reservoir is configured in this embodiment as a piston reservoir with a reservoir piston (18c1) (separating element), and this piston reservoir defines a reservoir chamber (18c2) with a variable volume. For this purpose, the reservoir piston (18c1) is displaceably accommodated inside a reservoir cylinder (18c4) so as to oppose the force of an elastic return device (18c3) configured, for example, as a coil spring.

[0025] In addition to the inlet (18c5) opening into the storage chamber (18c2), the pressure medium storage device (18) has an outlet (18c6) opening out of the storage chamber (18c2). The outlet (18c6) is located upstream of the second pressure generator (18e) of the brake pressure modulator (18) and is in contact with the brake circuit (10) in a manner controllable by a return valve (18d). This second pressure generator (18e) is operable by external force from the drive engine (18f), and when the second pressure generator (18e) is operated, the pressure medium is pumped from the master brake cylinder (12) through the first directional control valve (18a) or inlet valve, which is open at that time, to the wheel brake (16), thereby causing pressure to build up within the wheel brake (16).

[0026] Upstream of the point where the outlet (18c6) of the pressure medium reservoir (18c) is connected to the brake circuit (10), there is an electrically controllable so-called second directional control valve (20) or high-pressure switching valve (20a). This high-pressure switching valve (20a) is provided to disconnect the master brake cylinder (12a) or the first pressure generator (12) from the brake circuit (10) when the second brake pressure generator (18e) is used to build up brake pressure within the wheel brake (16). Therefore, the second directional control valve (20) controls the first pressure medium connection (22) that leads from the master brake cylinder (12a) or the first brake pressure generator (12) to the second brake pressure generator (18e).

[0027] A third directional control valve (24) or pressure control valve (24a) is provided to control the brake pressure in the brake circuit (10) generated by the second brake pressure generator (18e). The third directional control valve (24) or pressure control valve (24a) is located in a second pressure medium connection (26), through which the second brake pressure generator (18e) is connected to a master brake cylinder (12a) or a first brake pressure generator (12).

[0028] The electrical control of the directional control valves (18a; 20, 24) and the electrical control of the electric motor (18f) of the second brake pressure generator (18e) are carried out as needed by the electronic control device (28) of the brake mechanism, that is, in accordance with the slip condition present on the wheel associated with one of the wheel brakes (16).

[0029] According to the present invention, a directional control valve (20) is used which is configured to be open in a current-free state. This directional control valve is configured as a proportional control valve and includes two hydraulic ports, and can be moved from a flow-through position (basic position) at multiple intermediate positions to a shut-off position by electrical control.

[0030] Therefore, in the basic position, that is, when the second directional control valve (20) is not electrically controlled, a consistent hydraulic connection exists between the first brake pressure generator (12) and the second brake pressure generator (18e), or between the point where the outlet (18c6) of the pressure medium reservoir (18c) merges with the brake circuit (10) and the first brake pressure generator (12). As a result, the pressure medium present in the reservoir chamber (18c2) of the pressure medium reservoir (18c) can be forced out toward the first brake pressure generator (12) by the release return device (18c3) of the pressure medium reservoir (18c). In other words, the pressure medium reservoir (18c) can spontaneously become empty when the brake system is switched off, for example, after a vehicle equipped with the brake system is parked and its drive engine is switched off.

[0031] The second directional control valve (20), which is open in the current-free state, is configured as a directional control valve with a single valve stage, and therefore has exactly one valve closure and a valve cross-section controlled by this valve closure (not shown). The opening of this directional control valve (20) is performed by mechanical force, and therefore does not require electrical control by an electronic control device (28), thus enabling such a low-cost valve structure. Furthermore, the single-stage directional control valve exerts a smaller throttling effect on the pressure medium flowing through the directional control valve compared to the multi-stage directional control valves known from the prior art, thereby improving the dynamics that can generate pressure changes in the brake circuit (10).

[0032] Aside from that, in the present invention, the third directional control valve (24) is also configured to be open in a current-free state. This third directional control valve (24) is also configured as a proportional control valve, has two ports, and may be capable of transitioning from any number of intermediate flow positions (basic positions) to shut-off positions by electrical control.

[0033] In the default position where no power is supplied, the third directional control valve (24) is open, and therefore a consistent hydraulic connection is formed from the second brake pressure generator (18e) to the first brake pressure generator (12).

[0034] The third directional control valve (24) is positioned within the second pressure medium connection (26) such that hydraulic bypass is impossible, and therefore all pressure medium introduced through the second pressure medium connection (26) flows through the third directional control valve (24). According to the present invention, the configuration of a bypass that bypasses the third directional control valve (24), as known from the prior art, is omitted, and a check valve for controlling the flow through such a bypass is also omitted. Therefore, in addition to component costs and assembly costs, structural space, which is already limited, is also saved.

[0035] Vehicles that have an electric motor in addition to an internal combustion engine as a drive system, i.e., so-called hybrid vehicles, or vehicles driven by an electric motor, can convert the vehicle's kinetic energy into electrical energy by switching the drive system from motor mode to generator mode during the braking process, and can also provide deceleration for the vehicle. Therefore, in such vehicles, the total brake torque corresponding to the driver's braking desire consists of the brake torque generated by the generator and the brake torque supplied by the brake system. However, the proportion of the total brake torque generated by the generator decreases as the vehicle speed decreases and must be compensated for by the correspondingly increasing proportion of the brake torque supplied by the brake system. This process is called brake torque mixing and is controlled by an electronic control device (28) of the brake mechanism and is carried out with little to no awareness to the driver or vehicle occupants.

[0036] Here, in a vehicle driven by an electric motor, if the driver increases the initial braking force during the braking process by applying strong force to the pedal or lever, i.e., the operating element (14) of the first brake pressure generator (12), the brake mechanism according to the present invention cannot reach the wheel brake (16) because there is no bypass to the third directional control valve (24). This is because the third directional control valve (24), which is normally used for this purpose, is electrically controlled by an electronic control device (28) during the braking process and is therefore in the closed position.

[0037] These drawbacks can be avoided by controlling the brake mechanism according to the present invention if a sensor device (30) that detects the brake pressure in the first brake pressure generator (12) or master brake cylinder (12a) and transmits a corresponding electrical signal to an electronic control device (28) of the brake mechanism is implemented in the brake mechanism according to the present invention. The control device recognizes the pressure rise within the framework of signal evaluation and, based on this, terminates the electrical control of the second directional control valve (20) or high-pressure switching valve (20a) and / or the electrical control of the third directional control valve (24) or pressure control valve (24a). Based on this, the directional control valves (20, 20a; 24, 24a) open, thereby transmitting the pressure in the first brake pressure generator (12), which is higher than the predominantly present pressure in the brake circuit, to the wheel brake (16). Simply put, in the present invention, the function of a check valve known from the prior art in the bypass for the third directional control valve (24) is realized by a control method stored in an electronic control device (28).

[0038] Naturally, modifications or additions beyond the above description can be considered in the above embodiments without thereby departing from the scope of protection of the present invention as defined by the claims.

Claims

1. An electronically slip-controllable brake mechanism for automobiles, A first brake pressure generator (12) for generating brake pressure in a brake circuit (10) to which a wheel brake (16) is connected, depending on the current braking requirement, A brake pressure modulator (18) for modulating the brake pressure in the wheel brake (16) depending on the current slip in the wheel associated with one of the wheel brakes (16), A second brake pressure generator (18e) is drivable by an electric motor and connected to the brake circuit (10) in parallel with the first brake pressure generator (12), At least one electrically controllable first directional control valve (18a) for controlling the supply of pressure medium to the wheel brake, A pressure medium storage container (18c) for storing the pressure medium that has flowed out from the wheel brake (16) in a storage chamber (18c2) of a storage cylinder (18c4), the pressure medium storage container (18c) having a separation member (18c1) inside that is movable against the force of an elastic return device (18c3), A brake pressure modulator (18) having, A first pressure medium connection section (22) from the first brake pressure generator (12) to the second brake pressure generator (18e), An electrically controllable second directional control valve (20) for controlling the first pressure medium connection (22), The drive mechanism (18f) of the second brake pressure generator (18e), and an electronic control device (28) for electrically controlling the first directional control valve (18a) and the second directional control valve (20) according to demand, In an electronically slip-controllable brake mechanism, The second directional control valve (20) is configured as a valve that is open when there is no current. A brake mechanism characterized by electronic slip control.

2. The second directional control valve (20) has exactly one valve control stage, each comprising a valve closing body and a valve cross section controlled by the valve body. The electronically slip-controllable brake mechanism according to claim 1, characterized in that

3. The brake mechanism includes an electrically controllable third directional control valve (24) for controlling the second pressure medium connection (26) from the second brake pressure generator (18e) to the first brake pressure generator (12), The third directional control valve (24) is positioned such that all pressure medium introduced through the second pressure medium connection (26) flows through the second directional control valve (24) and that hydraulic bypass flow is impossible within the second pressure medium connection (26). An electronically slip-controllable brake mechanism according to claim 1 or 2, characterized in that

4. The second directional control valve (20) and the third directional control valve (24) are configured as proportional valves, and the proportional valves are capable of transitioning from a normally open basic position to a shut-off position at multiple intermediate positions through which the pressure medium flows, by electrical control by the electronic control device (28). The electronically slip-controllable brake mechanism according to claim 2, characterized in that

5. The second directional control valve (20) is positioned in the brake circuit (10) upstream of the outlet (18c6) of the pressure medium storage devices (18c) (18e) that opens to the brake circuit (10). An electronically slip-controllable brake mechanism according to any one of claims 1 to 4, characterized in that

6. In an automobile equipped with an electric drive engine, a method for controlling an electronically slip-controllable brake mechanism according to any one of claims 1 to 5, An electrical sensor signal is supplied from the pressure detection sensor device (30) in the first pressure generator (12) to the electronic control device (28). During the braking process in which brake pressure is generated in the wheel brake (16) by the second brake pressure generator (18e), if the evaluation of the sensor signal indicates that the driver has increased his braking desire, the electronic control device (28) controls the second directional control valve (20) and / or the third directional control valve (24) so ​​that at least one of the second directional control valve (20) or the third directional control valve (24) takes a flow position. A method characterized by the following:

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