Electro-hydraulic dual-circuit braking system

Abstract

The invention relates to an electro-hydraulic dual-circuit brake system, comprising at least one brake fluid reservoir (10), a master brake cylinder (12) with at least one piston (14, 50) for actuating a piston-cylinder unit (16), the cylinder (18) of which is connected to the brake fluid reservoir (10), the piston-cylinder unit (16) comprising a first piston (20) which is displaceable in the cylinder (18) of the piston-cylinder unit (16) by means of a first motor (24) to generate hydraulic brake pressure, and a second piston (22) which is displaced in the cylinder (18) by hydraulic pressure exerted by the first piston (20) or mechanically by the two pistons (20, 22) coming into contact with each other, and comprising two brake circuits (S1, S2) which are hydraulically separated from each other by the second piston (22) and connected to the cylinder (18) of the piston-cylinder unit (16).wherein at least one valve (32, 34, 36) is interposed between the master brake cylinder (12) and the piston-cylinder unit (16), through which a fluid connection between the master brake cylinder (12) and the piston-cylinder unit (16) can be established when the at least one valve (32, 34, 36) is de-energized.

Description

[0001] The invention relates to an electro-hydraulic dual-circuit brake system with at least one brake fluid reservoir, with a master brake cylinder with at least one piston for actuating a piston-cylinder unit, the cylinder of which is connected to the brake fluid reservoir, which has a first piston which can be displaced in the cylinder of the piston-cylinder unit by means of a first motor to generate a hydraulic brake pressure, and a second piston which is displaced in the cylinder by hydraulic pressure application by the first piston or mechanically by the two pistons coming into contact with one another, with two brake circuits which are connected to the cylinder of the piston-cylinder unit in a hydraulically separated manner by the second piston. State of the art

[0002] Electrohydraulic braking systems generate hydraulic brake pressure to actuate hydraulic wheel brakes using external power. For example, a piston is moved by an electric motor via a screw drive in a cylinder. A muscle-powered master brake cylinder for alternative actuation of the power brake system is provided, in particular, for the purpose of auxiliary braking, for example, in the event of a failure of the electric motor or its power supply.

[0003] Such power braking systems are known from EP 1 970 271 A1 and EP 2 641 788 A1, with the special feature that the cylinder for the power braking is designed as a dual-circuit cylinder for a hydraulically separated connection of two brake circuits, like a master brake cylinder of a hydraulic dual-circuit vehicle brake system. Like a dual-circuit master brake cylinder, the cylinder for the power braking in the two patent applications also has two pistons arranged coaxially one behind the other and at a distance from each other in the cylinder, of which a first piston, also referred to as the primary piston or rod piston, is displaced in the cylinder by an electric motor via a ball screw drive, and a second piston, also referred to as the secondary piston or floating piston, is acted upon by the hydraulic brake pressure generated by the first piston, whereby the second piston generates the same brake pressure.

[0004] The object of the invention is to provide a dual-circuit braking system which, in a structurally simple manner, allows a reliable mechanical braking effect even in the event of failure of the electrically controlled braking. Disclosure of the invention

[0005] This object is achieved according to the invention by an electro-hydraulic dual-circuit brake system having the features of claim 1. Preferred embodiments of the invention are specified in the subclaims.

[0006] According to the invention, valve types are preferably used in the electro-hydraulic dual-circuit brake system, which are referred to as follows: CSV (Currentless Switching Valve) A valve that is open when de-energized and can be switched open or closed in one step, allowing bidirectional flow. This valve is used to connect or disconnect a hydraulic connection between individual components of the braking system.

[0007] SSV (Separating Switching Valve) is a valve that is normally closed and can be switched open or closed in two steps, allowing bidirectional flow. This valve is used to separate the hydraulic-mechanical and electric pedal operation of a braking system.

[0008] BSV valve, which serves as a check valve between individual components of the brake system.

[0009] The electro-hydraulic dual-circuit brake system according to the invention has at least one brake fluid reservoir and a master brake cylinder with at least one piston for actuating a piston-cylinder unit, the cylinder of which is connected to the brake fluid reservoir. The piston-cylinder unit has a first piston, which is displaceable in the cylinder of the piston-cylinder unit with a first motor, in particular an electric motor with a rotation / translation converter gear, to generate hydraulic brake pressure, and a second piston, which is displaced in the cylinder by hydraulic pressure applied by the first piston or mechanically by the two pistons contacting one another. Two brake circuits are provided, which are connected to the cylinder of the piston-cylinder unit in a hydraulically separated manner by the second piston.According to the invention, at least one valve is interposed between the master brake cylinder and the piston-cylinder unit, by means of which a fluid connection can be established between the master brake cylinder and the piston-cylinder unit when the at least one valve is de-energized, wherein a fluid connection then exists between the master brake cylinder and the piston-cylinder unit.

[0010] According to the invention, a braking system with redundancy and hydraulic backup for the actual electrical actuation is created. The braking system according to the invention can have one or more power supplies; with an extension of two power supplies each, the braking system according to the invention can even be suitable for HAD applications from levels 3 to 5.

[0011] The invention thus provides a structurally simple implementation of a decoupled system with mechanical backup, preferably using three valves, while maintaining the same functionality as known braking systems, particularly with a sequential arrangement of the two pistons of the piston-cylinder unit for a decoupled system with mechanical backup and circuit separation by means of the first piston and the second piston, with the first piston being directly connected to the first electric motor. Preferably, a return spring acts on the second piston, with an end stop as a stroke limiter.

[0012] According to a structurally particularly simple preferred embodiment of the electro-hydraulic dual-circuit brake system according to the invention, the at least one valve consists of a first valve CSV1, preferably designed as a currentless switching valve, which is open when de-energized, in particular can be switched open or closed in one step and is assigned to the first brake circuit S1, of a second valve CSV2, preferably designed as a currentless switching valve, which is open when de-energized, in particular can be switched open or closed in one step and is assigned to the second brake circuit S2 and a third valve SSV, preferably designed as a separating switching valve, which is closed when de-energized and in particular open in two steps, whereby a bidirectional flow is made possible therethrough.

[0013] The third valve SSV is preferably arranged between the brake fluid reservoir and the first valve or between the brake fluid reservoir and the second valve.

[0014] According to the invention, a first check valve BSV1 can also be arranged between the brake fluid reservoir and the piston-cylinder unit and can be assigned to the first brake circuit S1.

[0015] According to the invention, a second check valve BSV2 can also be arranged between the brake fluid reservoir and the piston-cylinder unit and can be assigned to the second brake circuit S2.

[0016] An embodiment of the invention with a first and / or second check valve BSV1, BSV2 allows a particularly flexible control of the piston-cylinder unit of the electro-hydraulic dual-circuit brake system.

[0017] The master brake cylinder can be designed as a monocylinder with one piston MC1 or, also advantageously, as a dual cylinder with one piston MC1 and another piston MC2, which offers particularly flexible adaptation to different areas of application.

[0018] According to an embodiment of the invention, additional fluid connections are provided between the brake fluid reservoir and the piston-cylinder unit, the first of which is provided in a fluid-conducting manner between the brake fluid reservoir and the first piston, assigned to the first brake circuit S1, and the second of which is provided in a fluid-conducting manner between the brake fluid reservoir and the second piston, assigned to the second brake circuit S2. This can particularly preferably, for example, create a circuit-separated fluid line on the suction side between the brake fluid reservoir and the first piston or between the brake fluid reservoir and the second piston, for example, via sniffer bores, which are respectively assigned to the respective pistons.

[0019] Furthermore, a preferred embodiment of the electro-hydraulic dual-circuit brake system according to the invention is particularly flexible with regard to switching between mechanical and electrical brake actuation, wherein the master brake cylinder can be actuated via a pedal, namely mechanically directly or electrically via a sensor system.

[0020] Finally, the invention also prefers an electro-hydraulic dual-circuit brake system in which the first piston is connected to the rotary / translational converter in a tension- and compression-resistant manner, such that the first piston, together with the first electric motor, can be displaced in two opposite directions within the cylinder of the piston-cylinder unit via the rotary / translational converter. This allows for structurally simple and reliable operation. Short description of the drawings

[0021] The invention will be explained in more detail below with reference to the embodiments shown in the drawings. Fig. 1 shows a schematic hydraulic circuit diagram according to a first embodiment of an electro-hydraulic dual-circuit brake system according to the invention; Fig. 2 shows a schematic hydraulic circuit diagram according to a second embodiment of an electro-hydraulic dual-circuit brake system according to the invention; Fig. 3 shows a schematic hydraulic circuit diagram according to a third embodiment of an electro-hydraulic dual-circuit brake system according to the invention; Fig. 4 shows a schematic hydraulic circuit diagram according to a fourth embodiment of an electro-hydraulic dual-circuit brake system according to the invention; and Fig. 5 a schematic hydraulic circuit diagram according to a fifth embodiment of an electro-hydraulic dual-circuit brake system according to the invention. Embodiments of the invention

[0022] The Fig. The electro-hydraulic dual-circuit brake system shown in Figure 1 comprises a piston-cylinder unit 16 with a cylinder 18 in which, as in a conventional, muscle-operated dual-circuit master brake cylinder, two pistons, a first piston 20 and a second piston 22, are displaceably arranged. To generate hydraulic brake pressure using external power, the first piston 20 is displaceable in the cylinder 18 via a helical gear with a first electric motor 24. In the exemplary embodiment, the helical gear is a ball screw drive, which can generally be understood as a rotation / translation converter gear 26. A reduction gear (not shown), in particular a planetary gear, can be arranged between the first electric motor 24 and the gear 26.According to the invention, the first electric motor 24, the transmission 26 and - if present - the reduction gear are arranged coaxially with the piston-cylinder unit 16, that is to say coaxially with the cylinder 18 and with the two pistons 20, 22, whereby the invention does not fundamentally exclude other arrangements of the first electric motor 24, the transmission 26 and, if present, the reduction gear with respect to the piston-cylinder unit 16, the cylinder 18 and the pistons 20, 22.

[0023] The hydraulic brake pressure generated by the first piston 20 in the cylinder 18 acts on an end face or piston surface of the second piston 22 facing the first piston 20, which is referred to here as the rear face 28 of the second piston 22, whereby the second piston 22 is displaced in the cylinder 18 and generates a hydraulic brake pressure on its side or piston surface facing away from the first piston 20, which is referred to here as the front face 30 of the second piston 22.

[0024] If the first piston 20 does not generate pressure in the cylinder 18 during its displacement - for example as a result of a leak - it strikes the second piston 22 during its displacement and displaces it mechanically by its contact with it, so that in this case too the second piston 22 generates a hydraulic braking pressure in the cylinder 18 on its front side 30.

[0025] On the cylinder 18 of the piston-cylinder unit 16, a pressureless brake fluid reservoir 10 is arranged, to which the cylinder 18 is connected between the two pistons 20, 22 and on the front side 30 of the second piston 22.

[0026] The brake system according to the invention is designed as a dual-circuit brake system with two brake circuits S1, S2 and—not shown in the exemplary embodiment—four hydraulic wheel brakes, two of which are each connected to a brake circuit S1, S2. A first of the two brake circuits S1 is connected between the two pistons 20, 22 to the cylinder 18 of the piston-cylinder unit 16 in such a way that the first brake circuit S1 is subjected to the hydraulic brake pressure generated by the first piston 20 during its displacement in the cylinder 18. The second brake circuit S2 is connected to the cylinder 18 of the piston-cylinder unit 16 on the front side 30 of the second piston 22 and is subjected to the brake pressure generated by the second piston 22 or which prevails on the front side 30 of the second piston 22 in the cylinder 18.

[0027] The second piston 22, on the rear side 28 of which the first brake circuit S1 and on the front side 30 of which the second brake circuit S2 are connected to the cylinder 18 of the piston-cylinder unit 16, hydraulically separates the two brake circuits S1, S2 from each other.

[0028] According to the invention, at least one valve 32, 34, 36 is interposed between a master brake cylinder 12 with at least one piston 14 MC1 for actuating the piston-cylinder unit 16 and the piston-cylinder unit 16, by means of which valve(s) a fluid connection can be established between the master brake cylinder 12 and the piston-cylinder unit 16 when the at least one valve 32, 34, 36 is de-energized, e.g. in the event of a power supply failure of the brake system, i.e. in the event that no hydraulic brake pressure is generated using external force, in which case according to the invention there is a fluid connection between the master brake cylinder 12 and the piston-cylinder unit 16. The valve 32 is a CSV1 valve, the valve 34 is a CSV2 valve and valve 36 is an SSV valve.

[0029] Between the brake fluid reservoir 10 RSV1 RSV2 and the piston-cylinder unit 16, additional fluid connections are also provided, the first of which is provided in a fluid-conducting manner between the brake fluid reservoir 10 RSV1 and the first piston 20, assigned to the first brake circuit S1, and the second of which is provided in a fluid-conducting manner between the brake fluid reservoir 10 RSV2 and the second piston 22, assigned to the second brake circuit S2. The connection to the respective pistons 20, 22 then preferably exists on the suction side via sniffer bores assigned to the respective pistons 20, 22.

[0030] This essentially results in the following functional principle of the electro-hydraulic dual-circuit braking system according to the invention.

[0031] When pressure is built up during normal operation, the generation of hydraulic brake pressure with external force transmits the driver's braking request, e.g., via the electric pedal 40, via sensors 42 to actuate the first electric motor 24. An automatic braking request from a system (level 3, 4 or 5) is carried out using the same logic. The valves 32 CSV1 and 34 CSV2 are closed and the valve 36 SSV is open. The first electric motor 24 rotates and the first piston 20 moves forward (towards the right in Fig. 1). The second piston 22, designed as a floating piston, moves forward (towards the right in Fig. 1) against the spring force of a return spring 44. Thus, the same pressure prevails in both circuits S1 and S2. Not shown is that in the two circuits S1 and S2, an ESP hydraulic volume is distributed to the 4 wheels via two connections, whereby the brake force is distributed via ESP valves in a manner known per se with an ESP / ABS control, and the volume generates pressure in the wheel calipers, so that the brake shoes close and press against the brake discs, thereby generating the braking effect. The brake is released by the backward movement of the first piston, whereby the spring force of the return spring 44 presses on the second piston 22 and thus this floating piston up to the stop (in Fig. 1 to the left). The pressures prevailing in the two circuits S1 and S2 are also identical when the brake is released. It should be noted that both the two circuits S1 and S1, as well as the first piston 20 and the second piston 22, are always hydraulically separated from each other via the piston seals of the first piston 20 and the second piston 22.

[0032] In the event of thermal stress, thermal relief can be achieved via sniffing holes. The system can also be filled this way. Both are well known and will not be described further here.

[0033] In the event of a fault, the following operating principle according to the invention generally applies: In the event of failure of the actuation, for example due to a power failure, both the first piston 20 and the second piston 22 are moved to the stop position (in the illustration of the Fig. 1 to the left).

[0034] The pressure build-up in circuit S1 occurs when the ESP (not shown) of S1 draws hydraulic fluid into circuit S1 via the sniffer bore at the first piston 20 and the first check valve 46 BSV1. The pressure build-up in circuit S2 occurs when the ESP (not shown) of S2 draws hydraulic fluid into circuit S2 via the sniffer bore at the second piston 22. The pressure reduction in circuit S1 occurs when the piston 14 MC1 in the master brake cylinder 12 is pushed to the stop (in Fig. 1 to the left) and thus allows a fluid connection to the brake fluid reservoir 10 RSV1. The pressure reduction in circuit S2 takes place when the second piston 22 is pushed to the stop (in Fig. 1 to the left) and thus allows a fluid connection to the brake fluid reservoir 10 RSV2.

[0035] Thus, according to the invention, the mechanical back up is provided via the fluid connection via the first Fig. 1 shown embodiment as a monocylinder with a piston 14 designed master brake cylinder 12 and the first valve 32 CSV1 and the second valve 34 CSV2.

[0036] In the event of a leak in circuit S1, the following operating principle according to the invention generally applies: A pressure build-up in circuit S1 is not possible due to the fault there. The pressure build-up in circuit S2 occurs when the first piston 20 is moved upon actuation of the piston 14 MC1 in the master brake cylinder 12, thus also pushing the second piston 22 forward (in Fig. 1 to the right). The pressure reduction in circuit S1 is not possible or not provided for due to the error there. The pressure reduction in circuit S2 takes place when the second piston 22 is pushed to the stop by the return spring 44 (in Fig. 1 to the left) and hydraulic fluid is pushed back into the brake fluid reservoir 10 RSV2.

[0037] In the event of a leak in circuit S2, the following operating principle according to the invention generally applies: The pressure build-up in circuit S1 occurs when the first piston 20 is moved upon actuation of the piston 14 MC1 in the master brake cylinder 12 (in Fig. 1 to the right). The second piston 22 is also pushed forward, but the seal between circuit S1 and circuit S2 is maintained, since the second piston 22 is at the stop (in Fig. 1 to the right) is still sealed. Pressure build-up in circuit S2 is not possible due to the error there. The pressure reduction in circuit S1 occurs when the first piston 20 moves back (in Fig. 1 to the left) and the hydraulic fluid pressure is reduced via the first valve 32 RSV1. Pressure reduction in circuit S2 is not possible or not provided for due to the fault there.

[0038] In the event of a fault in which the electrical actuation fails during the pressure build-up during the braking process, the following functional principle according to the invention generally results: The first piston 20 remains (initially) stationary. The first valve 32 CSV1 opens, since it is de-energized. The hydraulic pressure from circuit S1 can escape. The second piston 22 is returned to its stop position (in Fig. 1 to the left). The pressure build-up in circuit S1 takes place via the first check valve 46 BSV1. The pressure build-up in circuit S2 takes place via the shovel bore at the second piston 22 or via a second check valve 48 BSV2 (in Fig. 1, Fig. 2 and Fig. 5 not shown; in Fig. 3 and Fig. 4). The pressure reduction in circuit S1 occurs via the first valve 32 CSV1. The pressure reduction in circuit S2 occurs via the sniffer bore at the second piston 22 and via the second valve 34 CSV2.

[0039] If the ESP should fail in circuit S1 and / or in circuit S2, according to the invention a brake pressure can still be built up in both circuits S1 and S2, whereby the failure of the ESP may at most limit the modulation of the brake pressure.

[0040] If overloading can lead to thermal expansion of the hydraulic fluid, thus stopping the brake movement, hydraulic fluid can expand to the brake fluid reservoir 10 RSV1 RSV2. Movement of the first piston 20 and the second piston 22 remains possible in principle.

[0041] This in connection with the Fig. The functional principle described in the first embodiment of the electro-hydraulic dual-circuit brake system according to the invention shown in Figure 1 also applies in principle to the other embodiments of the electro-hydraulic dual-circuit brake system shown.

[0042] The second embodiment of the electro-hydraulic dual-circuit brake system according to the invention according to Fig. 2 differs from that in Fig. 1 shown first embodiment essentially in that the third valve 36 SSV is assigned to the first valve 32 CSV1 and thus to the first circuit S1 and not, as in Fig. 1, the second valve 34 CSV2 and thus the second circuit S2.

[0043] The third embodiment of the electro-hydraulic dual-circuit brake system according to the invention Fig. 3 differs from that in Fig. 2 shown second embodiment and thus further from that shown in Fig. 1 shown first embodiment essentially in that the brake fluid reservoir 10 RSV2 can be brought into fluid connection with the second circuit S2 via a second check valve 48 BSV2.

[0044] The fourth embodiment of the electro-hydraulic dual-circuit brake system according to the invention Fig. 4 differs from those in the Fig. 1, Fig. 2 and Fig. 3 essentially in that the master brake cylinder 12 is not designed as a monocylinder with a piston 14, but as a dual cylinder with a piston 14 MC1 and a further piston 50 MC2.

[0045] The fifth embodiment of the electro-hydraulic dual-circuit brake system according to the invention according to Fig. 5 corresponds to the Fig. 4 shown fourth embodiment with dual cylinder and differs from the one in Fig. 4 shown fourth embodiment essentially in that - as in the figures shown in the Fig. 1 and Fig. 2 - no second check valve 48 BSV2 is provided.

[0046] Otherwise, the braking systems are designed in the same way as in the figures, so that the same reference numerals in the figures describe the same features. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 1 970 271 A1

[0003] EP 2 641 788 A1

[0003]

Claims

[1] An electro-hydraulic dual-circuit brake system, comprising at least one brake fluid reservoir (10), a master brake cylinder (12) with at least one piston (14, 50) for actuating a piston-cylinder unit (16), the cylinder (18) of which is connected to the brake fluid reservoir (10), which has a first piston (20) which is displaceable in the cylinder (18) of the piston-cylinder unit (16) by a first motor (24) to generate a hydraulic brake pressure, and a second piston (22) which is displaced in the cylinder (18) by hydraulic pressure application by the first piston (20) or mechanically by the two pistons (20, 22) being in contact with one another, with two brake circuits (S1, S2) which are connected hydraulically separated from one another to the cylinder (18) of the piston-cylinder unit (16) by the second piston (22), characterized bythat at least one valve (32, 34, 36) is fluidly interposed between the master brake cylinder (12) and the piston-cylinder unit (16), by means of which valve a fluid connection can be established between the master brake cylinder (12) and the piston-cylinder unit (16) when the at least one valve (32, 34, 36) is de-energized. [2] Electro-hydraulic dual-circuit braking system according to claim 1, characterized by in that the at least one valve (32, 34, 36) is designed with a first valve (32) which is normally open and is assigned to the first brake circuit (S1), with a second valve (34) which is normally open and is assigned to the second brake circuit (S2) and with a third valve (36) which is normally closed, whereby a bidirectional flow is made possible therethrough. [3] Electro-hydraulic dual-circuit braking system according to claim 2, characterized bythat the third valve (36) is arranged in a fluid-conducting manner between the brake fluid reservoir (10) and the first valve (32). [4] Electro-hydraulic dual-circuit braking system according to claim 2, characterized by that the third valve (36) is arranged in a fluid-conducting manner between the brake fluid reservoir (10) and the second valve (34). [5] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 4, characterized by that a first check valve (46) is arranged between the brake fluid reservoir (10) and the piston-cylinder unit (16) and is assigned to the first brake circuit (S1). [6] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 5, characterized by that a second check valve (48) is arranged between the brake fluid reservoir (10) and the piston-cylinder unit (16) and is assigned to the second brake circuit (S2). [7] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 6, characterized by that there are additional fluid connections between the brake fluid reservoir (10) and the piston-cylinder unit (16), fluid-conducting to the first between the brake fluid reservoir and the first piston (20), assigned to the first brake circuit (S1), and fluid-conducting to the second between the brake fluid reservoir (10) and the second piston (22), assigned to the second brake circuit (S2). [8] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 7, characterized by that the master brake cylinder (12) is designed as a monocylinder with one piston (14). [9] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 7, characterized by that the master brake cylinder (12) is designed as a dual cylinder with a piston (14) and a piston (50). [10] Electro-hydraulic dual-circuit braking system according to one of claims 1 to 9, characterized by that the first piston (20) is connected to the rotation / translation converter gear (26) in a tensile and compressive manner such that the first piston (20) is displaceable with the first motor (24) in two opposite directions in the cylinder (18) of the piston-cylinder unit (16).

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