DE102017219964A1 - Electrohydraulic actuator and method for operating an electrohydraulic actuator - Google Patents

Abstract

The invention relates to an electrohydraulic actuator (1) for a brake system, comprising an electric motor (2) with a rotor and a stator, a cylinder (3) in which a pressure piston (4) is displaced, wherein the pressure piston (4) via a Transmission (7) is coupled to the rotor of the electric motor (2), with a first hydraulic pressure chamber (5) which is delimited by a first active surface of the pressure piston (4), and one on the first pressure chamber (5) opposite side of the Pressure piston (4) arranged second hydraulic pressure chamber (6), which is bounded by a second active surface of the pressure piston (4), wherein the second effective surface of the pressure piston (4) is smaller than the first effective area of the pressure piston (4), wherein the transmission ( 7) is such that a rotational movement of the rotor is converted in a constant sense of rotation in repeated forward and backward translation movements of the pressure piston (4). The invention also relates to methods for operating an electro-hydraulic brake system with an electro-hydraulic actuator.

Description

The invention relates to an electrohydraulic actuator for a brake system, comprising an electric motor with a rotor and a stator, a cylinder in which a pressure piston is displaced, wherein the pressure piston is coupled via a gear to the rotor of the electric motor, with a first hydraulic pressure chamber, which is delimited by a first effective area of the pressure piston, and a second hydraulic pressure chamber arranged on the side of the pressure piston opposite the first pressure space, which is delimited by a second effective area of the pressure piston, the second effective area of the pressure piston being smaller than the first effective area of the pressure piston , The invention also relates to a method for operating an electro-hydraulic brake system with an electro-hydraulic actuator and at least one wheel brake.

From the DE 10 2011 080 312 A1 a brake system for motor vehicles is known which comprises a pressure supply device with a double-acting piston-cylinder arrangement. The piston-cylinder arrangement can be actuated by means of an electric motor with the interposition of a rotation-translation gear.

Such a pressure-providing device has the disadvantage that a switching from a forward stroke of the piston to a backward stroke of the piston takes a certain amount of positioning time, since the direction of rotation of the motor must be changed. In addition, only one operating direction is possible if the piston is located at one end of its displacement.

Object of the present invention is therefore to provide an electro-hydraulic actuator for use in a brake system, which has a better availability and faster positioning.

According to the invention, the gear of the actuator is designed such that a rotational movement of the rotor is converted in a constant sense of rotation in repeated forward and reverse translation movements of the pressure piston. This has the advantage that continuous pressure can be provided. Interruptions of the pressure supply for sucking in pressure medium or to reverse the direction of rotation of the electric motor are not required. In addition, such a device is also particularly inexpensive to produce.

Thus, the forward and the return stroke of the pressure piston is used for the printing position. An electric motor can pass through in one direction and therefore be particularly simple.

Preferably, the power transmission between the transmission and the pressure piston via a push rod, which is immersed in the second pressure chamber and connected to the pressure piston. The effective area of the piston is reduced at a pressure build-up in the second pressure chamber by the cross-sectional area of the push rod. As a result, the second effective area is smaller than the first effective area.

The push rod is guided through the second pressure chamber and is fastened on the side of the piston facing the second pressure chamber. As a result, the reduction of the second effective area (the effective area of the pressure piston at a pressure build-up in the second pressure chamber) is effected.

Advantageously, the actuator comprises a displacement sensor, which is designed to detect a translation path of the pressure piston. The displacement sensor is preferably arranged on the pressure rod. The displacement sensor makes it possible to carry out volume balancing, since the movements of the pressure piston are tracked and therefore the displaced volume can be calculated. A volume balance enables a particularly accurate print position.

Preferably, the transmission comprises a connecting rod, by means of which the rotational movement of the rotor is converted in the constant direction of rotation in forward and reverse translation movements of the pressure piston. By using a connecting rod, the translation of one revolution of the motor into a translational path of the desired length can be implemented structurally in a particularly simple manner.

Alternatively, the transmission preferably comprises an eccentric, by means of which the rotational movement of the rotor is converted in the constant direction of rotation into forward and backward translational movements of the pressure piston. Eccentrics are a proven technology. Such a transmission is also particularly space-saving.

Alternatively, the gearbox preferably comprises a rocker arm, by means of which the rotational movement of the rotor is converted in the constant direction of rotation into forward and backward translational movements of the pressure piston.

Preferably, a first check valve is connected between the first pressure chamber and the second pressure chamber. When the pressure in the first pressure space is greater than the pressure in the second pressure space Pressure chamber, so opens the first check valve and connects the pressure chambers hydraulically.

Particularly preferably, the first check valve is arranged in a bore of the pressure piston. This design is particularly space-saving and leads to particularly short cable paths.

The invention also relates to a method for operating an electrohydraulic brake system having an electrohydraulic actuator and at least one wheel brake, in which the electric motor is operated with a constant sense of rotation of the rotor in order to build up pressure in the wheel brake by means of the actuator. Preferably, the first pressure chamber is connected via a first, electrically operable valve with a first brake line. The second pressure chamber is connected via a second, electrically operable valve with a second brake line and the first brake line is connected via a third, electrically operable valve with the second brake line. At least one wheel brake is hydraulically connected to the first brake line. In this way, the pressure chambers can each be connected to the first and second brake line, as well as each other by the valves are switched appropriately. A pressure in the wheel brake can be provided by means of the first or the second pressure chamber via the first brake line.

Particularly preferably, the first valve is designed to be normally closed. Preferably, the second valve is designed to be de-energized closed. Preferably, the third valve is executed normally closed. In this way, in the event that a power supply of the brake system fails, the actuator of the brake lines and thus separated from the wheel brakes.

Optionally, the first pressure chamber or the second pressure chamber can be hydraulically connected to one or more wheel brakes via the first and / or second brake line. The first and / or second pressure chamber can also be connected in each case with a pressure medium container so that pressure medium is discharged into the pressure medium container.

Advantageously, the first pressure chamber is connected via a second check valve with a pressure medium container and the second pressure chamber connected via a third check valve with the pressure medium container. The check valves are designed so that at a negative pressure in the respective pressure chamber brake fluid is sucked from the pressure fluid tank, while the check valves close each with built-up pressure in the respective pressure chamber and thus prevent backflow of pressure fluid through the respective check valve in the pressure fluid reservoir. In each case pressure medium is sucked out of the pressure medium container via the second and third check valves.

Preferably, pressure in the at least one wheel brake is optionally set by means of the first pressure chamber or by means of the second pressure chamber. Advantageously, a pressure chamber is selected for a braking operation at any time by a control unit, to be provided via the pressure.

Advantageously, the first, second and third valves are switched so that the selected pressure chamber is hydraulically connected to the wheel brake, so that pressure in the wheel brake is provided by the selected pressure chamber. Pressure that is built up during the countermovement in the other pressure chamber, can be derived in the pressure fluid reservoir.

Advantageously, the brake system is operated in so-called "by-wire" mode. A requested by the driver or an assistance system brake pressure is provided by the electro-hydraulic actuator.

Preferably, a brake pressure request to be provided by the actuator is classified into one of at least two categories. Pressure in the at least one wheel brake for brake requirements of the first category is provided by means of the first pressure space and pressure for brake pressure requirements of the second category is provided by means of the second pressure space.

Particularly preferably, brake pressure requirements are classified in the first category when the request for the brake fluid volume exceeds a first threshold value or a pressure requirement falls below a second threshold value.

Brake pressure requirements are particularly preferably classified in the second category if the requested braking system pressure in the at least one wheel brake is particularly high and only a small volume is required.

Particularly preferably, brake pressure requirements are classified into the second category when a pressure request exceeds a second threshold. This procedure is used, for example, in so-called brake fading.

Advantageously, the threshold value of the pressure requirement is designed to be approximately 50-60% of the maximum pressure of the actuator. This has the Advantage that without switching operations braking up to a delay of 1g with good dynamics are adjustable. The maximum pressure is preferably in the range 200-220 bar.

Preferably, the second threshold is about 120 bar.

Pressures below the second threshold value can thus be approached very dynamically by means of the first pressure chamber, moreover the pressure supply is switched over and pressure is provided by means of the second pressure chamber.

• 1 ein erstes Ausführungsbeispiel eines erfindungsgemäßen Aktuators,
• 2 ein zweites Ausführungsbeispiel eines erfindungsgemäßen Aktuators,
• 3 ein Ausführungsbeispiel eines erfindungsgemäßen Aktuators mit einem Getriebe mit einem Pleuel,
• 4 eine beispielsgemäße Ventilschaltung zur Anbindung eines Aktuators an Bremsleitungen.

The invention will be explained in more detail below in connection with the accompanying drawings of exemplary embodiments. Show it:

• 1 A first embodiment of an actuator according to the invention,
• 2 A second embodiment of an actuator according to the invention,
• 3 An embodiment of an actuator according to the invention with a transmission with a connecting rod,
• 4 an exemplary valve circuit for connecting an actuator to brake lines.

Like reference numerals designate like parts throughout the figures.

1 shows a first embodiment of an actuator according to the invention 1 , The actuator 1 includes a cylinder 3 in which a pressure piston 4 is arranged. The cylinder 3 is as a double-acting cylinder 3 running, with on each side of the pressure piston 4 a pressure medium filled pressure chamber is arranged.

The actuator 1 also includes an electric motor 2 with a rotor and a stator. About a not shown here transmission 7 The rotational movement of the rotor is converted into a translational movement. About a push rod 9 is the pressure piston 4 with the gearbox 7 coupled, allowing translational movement on the plunger 4 is transmitted. In this case, a rotational movement of the rotor in a constant rotational direction in a repeated reciprocating motion of the pressure piston 4 transformed.

The pressure piston 4 for example, by a gear 7 with a connecting rod 10 , an eccentric, a rocker arm, or a similar running device driven. Decisive here is that the engine keeps the same direction of rotation all the time.

The push rod 9 emerges, for example, in the second pressure chamber 6 one and is on the side of the pressure piston 4 which the second pressure chamber 6 facing, on the plunger 4 attached. This is the effective area of the plunger 4 at a pressure build-up in the second pressure chamber 6 around the cross-sectional area of the push rod 9 reduced. The pressure piston 4 is operable in both directions with different effective surfaces.

With a pushing movement of the push rod 9 becomes the pressure piston 4 in the direction of the first pressure chamber 5 moved and in the first pressure room 5 Pressure built up while in the second pressure chamber 6 a negative pressure is created and pressure medium is sucked. At a pulling movement of the push rod 9 is, however, in the second pressure chamber 6 Pressure built up and in the first pressure chamber 5 Drained pressure medium.

The first effective area 15 is the first pressure room 5 facing and acts at a pressure build-up in the first pressure chamber 5 , The second effective area 16 is the second pressure chamber 6 facing and acts at a pressure build-up in the second pressure chamber 6 ,

At constant engine torque or uniform rotation of the rotor in a constant direction is at each push movement of the push rod 9 in the first pressure room 5 built up in first pressure and moved a first volume. Each pull movement is in the second pressure chamber 6 built a second pressure, which due to the smaller effective area (second effective area 16 ) is greater than the first pressure. The corresponding shifted second volume is smaller than the first volume. The pressure piston 4 is always on the conveyor and can set different pressures with the same torque, combined with a correspondingly large or small volume.

Advantageously, the actuator comprises 1 a displacement sensor 14 , which is adapted to a translation path of the pressure piston 4 capture. The displacement sensor 14 is preferred on the push rod 9 arranged and detects the translational movement of the push rod 9 and thereby the translation of the pressure piston 4 , A combination with a displacement sensor 14 makes sense to make a volume accounting.

2 shows a second embodiment of an actuator according to the invention. In addition to the in 1 shown components of the actuator is a first check valve 8th between the first pressure chamber 5 and the second pressure chamber 6 connected. Exceeds the pressure in the first pressure chamber 5 the pressure in the second pressure chamber 6 What happens during a pushing movement of the push rod 9 this is the case, the first check valve opens 8th and pressure fluid flows from the first pressure chamber 5 in the second pressure chamber 6 , At a pulling movement of the push rod 9 closes the first check valve 8th , so in the second pressure chamber 6 a pressure is built up.

This construction allows a particularly simple design, in the pressure medium in the second pressure chamber 6 from the first pressure room 5 is sucked. A pressure supply is in this arrangement only by means of the second pressure chamber 6 possible.

The first pressure room 5 is via a second check valve 31 with a pressure medium container (not shown) connected and the second pressure chamber 6 is via a third check valve 32 also connected to the pressure fluid container.

Preferably, the first pressure chamber is connected via a fourth check valve to a brake line of the brake system and the second pressure chamber is connected via a fifth check valve with at least one brake line. About the brake line can be a pressure in at least one wheel brake 42 to be provided. In this way, each built in one of the pressure chambers pressure in the wheel brake 42 be controlled without having to control valves, while suction of brake fluid from the wheel brakes is prevented.

Preferably, the first check valve 8th in a bore of the pressure piston 4 arranged.

3 shows an embodiment of an actuator according to the invention with a transmission with a connecting rod. An exemplary transmission 7 , which with the embodiments of the 1 or 2 can be combined, is shown here in more detail.

A connecting rod 10 is, for example via a crank pin, with the rotor of the electric motor 2 coupled. About a joint is the connecting rod 10 with the push rod 9 connected. A rotational movement of the rotor is in this way in a translational movement of the push rod 9 transformed.

4 shows an exemplary valve circuit for the hydraulic connection of an exemplary actuator to brake lines.

The first pressure room 5 is via a first, electrically actuated valve 11 with a first brake line 21 connected. The second pressure chamber 6 is via a second, electrically actuated valve 12 with a second brake line 22 connected. Between the two braking powers is a third, electrically actuated valve 13 connected.

About the valves 11 . 12 . 13 and the brake lines 21 . 22 will be at least one wheel brake 42 the brake system supplied with pressure medium. The first brake line 21 has a connection 40 over which the wheel brake 42 can be supplied with braking means.

The second brake pipe 22 has a connection 41 , About the connection 41 At least one further wheel brake and / or a pressure medium container are preferably connected. Particularly preferred is at each of the terminals 40 . 41 each connected to a brake circuit of the brake system, each with at least one wheel brake.

In addition, the first pressure chamber 5 via a second check valve 31 with a pressure medium container (not shown) connected and the second pressure chamber 6 via a third check valve 32 also connected to the pressure fluid container.

By switching the valves 11 . 12 . 13 can each be the pressure chamber 5 . 6 which is to provide a requested pressure with the wheel brake 42 be connected, as long as by a translation of the pressure piston 4 a pressure in the pressure chamber 5 . 6 is built. At the opposite movement of the pressure piston 4 becomes the pressure room 5 . 6 by switching the valves 11 . 12 . 13 from the wheel brake 42 disconnected to a suction of brake fluid from the wheel brake 42 or to prevent brake lines. The brake fluid is sucked in via the check valves 31 . 32 from the pressure medium tank.

Further advantageous valve arrangements and connections of the actuator with the wheel brakes can DE 10 2011 080 312 A1 be removed. In this case, the first and second valves correspond 11 . 12 the Zuschaltventilen described there, via which the pressure chambers with brake circuits or input ports of intake valves are connectable.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 102011080312 A1 [0002, 0052]

Claims (11)

Electrohydraulic actuator (1) for a brake system, comprising an electric motor (2) with a rotor and a stator, a cylinder (3) in which a pressure piston (4) is displaced, the pressure piston (4) being connected via a transmission (7) is coupled to the rotor of the electric motor (2), with a first hydraulic pressure chamber (5), which is bounded by a first active surface of the pressure piston (4), and one on the first pressure chamber (5) opposite side of the pressure piston (4) arranged second hydraulic pressure chamber (6), which is bounded by a second active surface of the pressure piston (4), wherein the second effective surface of the pressure piston (4) is smaller than the first effective area of the pressure piston (4), characterized in that the transmission (7 ) is such that a rotational movement of the rotor is converted in a constant sense of rotation in repeated forward and reverse translation movements of the pressure piston (4). Electrohydraulic actuator (1) according to Claim 1 , characterized in that the actuator (1) comprises a displacement sensor (14) which is adapted to detect a translation path of the pressure piston (4). Electrohydraulic actuator (1) according to one of the preceding claims, characterized in that the force transmission between the gear (7) and the pressure piston (4) via a push rod (9), which is immersed in the second pressure chamber (6) and with the pressure piston (4) is connected, and that the second effective area of the pressure piston (4) by the cross-sectional area of the push rod (9) is reduced. Electrohydraulic actuator (1) according to one of the preceding claims, characterized in that the transmission (7) comprises a connecting rod (10) or an eccentric or a rocker arm, by means of which the rotational movement of the rotor in the constant direction of rotation in forward and reverse translation movements of the pressure piston (4) is converted. Electrohydraulic actuator (1) according to one of the preceding claims, characterized in that the first pressure chamber (5) via a first, electrically actuated, in particular normally closed, valve (11) with a first brake line (21) is connected, that the second pressure chamber (6) via a second, electrically actuated, in particular normally closed, valve (12) is connected to a second brake line (22) and that the first brake line (21) via a third, electrically actuated, in particular normally closed, valve (13) is connected to the second brake line (22). Electrohydraulic actuator (1) according to one of the preceding claims, characterized in that the first pressure chamber (5) via a second check valve (31) is connected to a pressure medium container and the second pressure chamber (6) via a third check valve (32) with the pressure medium container connected is. Electrohydraulic actuator (1) according to one of the preceding claims, characterized in that a first check valve (8) between the first pressure chamber (5) and the second pressure chamber (6) is connected, wherein the first check valve (8) opens and the pressure chambers hydraulically connects when the pressure in the first pressure chamber (5) is greater than the pressure in the second pressure chamber (6). Electrohydraulic actuator (1) according to Claim 7 , characterized in that the first check valve (8) in a bore of the pressure piston (4) is arranged. Method for operating an electrohydraulic brake system with an electrohydraulic actuator (1) according to one of the Claims 1 to 8th and at least one wheel brake (42), which is hydraulically connected to the actuator, characterized in that to build up pressure in the wheel brake (42) by means of the actuator of the electric motor (2) is operated with a constant sense of rotation of the rotor. Method according to Claim 9 , characterized in that pressure in the at least one wheel brake (42) is selectively adjusted by means of the first pressure chamber (5) or by means of the second pressure chamber (6). Method according to one of Claims 9 or 10 characterized in that a brake pressure request to be provided by the actuator (1) is classified into one of at least two categories and provides pressure in the at least one brake pressure (42) brake requirements of the first category by means of the first pressure space (5) and is provided for brake pressure requirements of the second category by means of the second pressure space (6).

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