Electromechanical brake booster, braking system, motor vehicle

Abstract

The invention relates to an electromechanical brake booster (1) with a gear assembly (2), in particular a spindle gear assembly, and with a return mechanism (3) configured to exert a return torque on the gear assembly (2) in order to return it to a predetermined rest position, wherein the return mechanism comprises at least one spring element (4). The spring element (4) is provided to have a first section (5) designed as a planar spiral spring and a second section (6) designed as a helical spring.

Description

[0001] The invention relates to an electromechanical brake booster, comprising a gear assembly, in particular a spindle gear assembly, and a return mechanism configured to exert a return torque on the gear assembly in order to return it to a predetermined rest position, wherein the return mechanism includes at least one spring element. The invention also relates to a brake system with such a brake booster and to a motor vehicle with such a brake system. State of the art

[0002] Brake boosters of the type mentioned above are known from the prior art. Such brake boosters require an automatic return mechanism. Typically, the return mechanisms used have one or more spring elements designed as coil springs, which exert corresponding axial return forces. The spring element is compressed, for example, when brake pressure builds up, by an actuator force from an actuator coupled to the transmission assembly and / or by a mechanically applied driver force (by actuating a brake pedal). The spring element, now pre-tensioned accordingly, can return the system to its initial or rest position when the corresponding actuator force and / or driver force ceases.In particular, the reset mechanism ensures that, in the event of a fault, the hydraulic pressure within a master brake cylinder operatively connected to the brake booster is reduced accordingly if the actuator can no longer be actuated. Reset mechanisms that exert restoring torques are also known.

[0003] For example, German patent application DE 10 2015 220 033 A1 discloses a braking device for a hydraulic motor vehicle braking system, comprising a master brake cylinder with a linearly displaceable piston therein, which generates brake pressure in a pressure chamber, wherein the piston can be actuated by an actuating element with an unamplified actuating force via a piston rod, an amplifier stage effectively upstream of the master brake cylinder, which acts on the piston with an amplifying force by means of a linearly displaceable force transmission element and has a housing, an electromechanical drive unit for driving the amplifier stage, a reset device for returning the amplifier stage to its unactuated initial position or rest position after a braking operation, wherein the reset device is forcibly pre-tensioned when the piston is actuated with the amplifying force, and wherein the reset device exerts a reset torque.which is essentially directed transversely to the piston's direction of movement. The return mechanism is implemented in particular with a spirally wound band spring.

[0004] German patent application DE 20 2016 101 914 U1 discloses a brake system designed as a drum brake with a helical spring, designed as a spiral torsion spring, associated with a planetary gear arrangement. The helical spring serves as a "self-locking" feature to prevent unwanted reverse drive of the planetary gear arrangement, which would lead to the release of an applied torque. Disclosure of the invention

[0005] The brake booster according to the invention, with the features of claim 1, is characterized in that the spring element comprises a first section designed as a planar coil spring and a second section designed as a helical spring. The combination of a coil spring and a helical spring in the same spring element, as provided for in the invention, advantageously ensures that the spring element exerts a particularly beneficial restoring torque.

[0006] In particular, the spiral spring is designed as a spiral band spring (“watch spring”), and the helical spring as a helical torsion spring. The brake booster preferably includes an electric actuator operatively connected to the transmission assembly, which is designed to generate a hydraulic brake pressure against a spring force of the spring element. The spring element advantageously ensures that, when the actuator is not actuated, the transmission assembly returns to its rest position due to the torque acting on the spring element when the actuator is actuated. The rest position is specifically defined such that the hydraulic pressure in a master brake cylinder operatively connected to the brake booster is at least approximately 0 bar.

[0007] According to a preferred embodiment of the invention, the sections are formed integrally. This integral construction advantageously ensures that the spring element is particularly robust. Alternatively, the sections are firmly connected to one another, for example, by a material bond, in particular by welding or bonding.

[0008] It is particularly preferred that a first winding end of the spring element is arranged in a housing groove of a brake booster housing. This arrangement in the housing groove offers the advantage that the spring element is securely fixed with respect to the brake booster. In particular, the first winding end is located at the first section.

[0009] According to a preferred embodiment of the invention, a second winding end of the spring element, particularly one facing away from the first winding end, is arranged on the gear assembly, especially on a bearing assembly. This arrangement on the gear assembly advantageously ensures that the spring element is operatively connected to the gear assembly, thus reliably transmitting the corresponding restoring torque. In particular, the second winding end is provided on the second section. Preferably, the winding end is arranged on a bearing sleeve of the bearing assembly, for example, inserted into a corresponding recess in the bearing sleeve. For example, the bearing sleeve is rotationally fixed to a spindle nut of the gear assembly.

[0010] It is particularly preferred that the first and / or second winding end(s) project radially from the spring element, in particular arranged offset from each other by a predetermined angle, preferably at right angles to each other. The radial projection of the respective winding end provides a particularly simple means of arrangement in relation to the brake booster or the transmission assembly, for example in the aforementioned housing groove or at the corresponding mounting position. In particular, the spring element has at least an approximately right-angled bend at the respective winding end, so that the winding end projects at a right angle with respect to a tangential direction. The offset arrangement, especially at right angles, preferably in an unpreloaded rest position of the spring element, offers the advantage that the connection of the respective winding ends is geometrically simple.

[0011] According to a preferred embodiment of the invention, the spring element has a constant and / or rectangular, in particular square, coil cross-section. A constant coil cross-section advantageously ensures that the restoring torque is exerted particularly uniformly. A rectangular coil cross-section allows for a particularly space-saving design of the spring element.

[0012] It is particularly preferred that the width of the coil cross-section in the radial extent of the spring element is greater than the height of the coil cross-section in the axial extent of the spring element, wherein the width and the height have a ratio of at least 3 to 2. With such a geometric design of the coil cross-section, an advantageously high restoring torque can be generated.

[0013] According to a preferred embodiment of the invention, the outer diameter of the first section in the relaxed state is larger than the outer diameter of the second section, wherein the outer diameters have a ratio of at least 3 to 2. The corresponding design of the outer diameters advantageously ensures that the sections are functionally distinct from one another, in particular that the first section is initially pre-tensioned with a torque when a corresponding actuator is actuated, as described above.

[0014] It is particularly preferred that the number of turns in the second section is greater than the number of turns in the first section, wherein, in particular, the number of turns in the first section is at least two and / or the number of turns in the second section is at least ten. With a corresponding configuration of the number of turns, the advantages of the spring element according to the invention are particularly pronounced. The number of turns in the second section is selected, in particular, depending on the available installation space and / or a predetermined distance to the gear assembly.

[0015] The braking system of a motor vehicle with the features of claim 10 is characterized by the brake booster according to the invention. This results in the advantages already mentioned.

[0016] The motor vehicle with the features of claim 11 is characterized by the braking system according to the invention. The advantages already mentioned also result from this.

[0017] Further preferred features and combinations of features will become apparent from the foregoing and from the claims. The invention will now be explained in more detail with reference to the drawings. These drawings show... Fig. 1. A first view of an advantageous brake booster, Fig. 2 a second view of the brake booster, and Fig. 3 a spring element of the brake booster.

[0018] Fig. 1 and Fig. Figure 2 shows detailed views of an advantageous brake booster 1 as part of a hydraulic brake system of a motor vehicle, which is not otherwise shown, wherein in the Fig. 1 a sectional view, and in the Fig. 2 shows a top view.

[0019] The brake booster 1 comprises a gear assembly 2, which in this case is designed as a spindle gear assembly, and a return mechanism 3. The return mechanism 3 is designed to exert a return torque on the gear assembly 2 in order to return it to a predetermined rest position. For this purpose, it comprises at least one spring element 4.

[0020] Spring element 4 is in the Fig. Figure 3 is shown separately and has a first section 5 designed as a planar spiral spring and a second section 6 designed as a helical spring. Sections 5 and 6 are firmly connected to each other, in particular formed in one piece.

[0021] The spring element 4 has a first coil end 7 and a second coil end 8 facing away from the first coil end 7. The first coil end 7 is located on the first section 5. The second coil end 8 is located on the second section 6.

[0022] The first and second winding ends 7, 8 each project radially from the spring element 4 or from the corresponding windings of the spring element 4, as shown in the Fig. 3 recognizable, wherein the winding ends 7, 8 are arranged offset from each other by a predetermined angle, in this case at least approximately perpendicular to each other.

[0023] The first winding end 7 projects radially outwards from the spring element 7, and the second winding end 8 projects radially into the spring element 4. The second winding end 8 thus extends into an interior space enclosed by the second section 6. According to a further embodiment, not shown, the second winding end 8 also extends outwards from the spring element 7.

[0024] In this case, the spring element 4 has at least an approximately right-angled bend at the respective winding end 7,8, so that the respective winding end 7,8 protrudes at a right angle with respect to a tangential direction.

[0025] The spring element 4 has a constant and rectangular coil cross-section. The width of the coil cross-section in the radial extent of the spring element 4 is greater than the height of the coil cross-section in the axial extent of the spring element 4, wherein the width and the height have a ratio of at least 3 to 2.

[0026] As especially in the Fig. As can be seen from Figure 3, the outer diameter of the first section 7 in the relaxed state is larger than the outer diameter of the second section 8, with the outer diameters having a ratio of at least 3 to 2. Furthermore, the number of turns in the second section 8 is greater than the number of turns in the first section 7, with the number of turns in the first section 7 being at least two and the number of turns in the second section 8 being at least ten.

[0027] The brake booster 1 further comprises a housing 9 in which the gear assembly 2 and the spring element 4 are arranged, at least partially. The housing 9 also has two housing grooves 10, each extending along an axial dimension of the gear assembly 2 and the spring element 4, and located diametrically opposite each other with respect to the housing 9 or a corresponding cavity in which the gear assembly 2 is received.

[0028] The gear assembly 2 comprises a spindle 11 and a rotatable spindle nut 12, wherein the spindle 11 is designed to be axially displaceable along the spindle nut 12. The spindle 11 is operatively connected, in particular, to an axially displaceable brake piston of a master brake cylinder connected to the brake booster 1, such that when it is displaced, the brake piston is also displaced, thereby generating hydraulic brake pressure in the brake system.

[0029] The spindle nut 12 is subjected to a restoring torque by the restoring mechanism 3, depending on the axial position of the spindle 11. To rotate the spindle nut 12, the brake booster 1 preferably has a controllable actuator, in particular an electric motor, which is operatively connected or coupled to the spindle nut 12 by means of the gear arrangement 2. The actuator is designed to generate a hydraulic brake pressure against a spring force of the spring element 4.

[0030] The spindle nut 12 is rotatably mounted by means of a bearing arrangement 13. The bearing arrangement 13 comprises a bearing element 14, in particular a ball bearing, and a bearing sleeve 15 arranged radially between the spindle nut 12 and the bearing element 14.

[0031] According to an alternative embodiment not shown, the spindle nut 12 is designed to be axially displaceable along the rotatable spindle 11, wherein the spindle 11 is subjected to a restoring torque by the restoring mechanism 3 depending on the axial position of the spindle nut 12. For rotating the spindle 11, a controllable actuator, in particular an electric motor, is preferably associated with it, as described above.

[0032] The first winding end 7 of the spring element 4 is arranged in one of the housing grooves 10, so that the winding end 7 is rotationally fixed to the housing 9. The second winding end 8 is coupled to the gear assembly 2, in particular to the bearing assembly 13. In this case, it is inserted in a corresponding groove or recess 18 of the bearing sleeve 15, which is rotationally fixed to the spindle nut 12, as shown in the Fig.Figure 2 shows the bearing sleeve 15 being axially extended in the direction of the second winding end 8 and thus extends completely through the spring element 4, or between the spring element 4 and the spindle 11.

[0033] The spindle 11 is designed as a hollow spindle to accommodate a plunger 17 connected to an input rod 16. The plunger 17 preferably connects an axially displaceable brake piston of a master brake cylinder connected to the brake booster 1 to the input rod 16, which is operatively connected, in particular, to an actuating device, for example, a brake pedal. The spindle nut 12 is also rotatably mounted about the input rod 16. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2015 220 033 A1

[0003] DE 20 2016 101 914 U1

[0004]

Claims

[1] Electromechanical brake booster (1), comprising a gear arrangement (2), in particular a spindle gear arrangement, and a return mechanism (3) configured to exert a return torque on the gear arrangement (2) in order to return it to a predetermined rest position, wherein the return mechanism comprises at least one spring element (4), characterized by , that the spring element (4) has a first section (5) designed as a planar spiral spring and subsequently a second section (6) designed as a helical spring. [2] Brake booster according to claim 1, characterized by , that sections (5,6) are formed in one piece together. [3] Brake booster according to any one of the preceding claims, characterized by , that a first winding end (7) of the spring element (4) is arranged in a housing groove (10) of a housing (9) of the brake booster (1). [4] Brake booster according to any one of the preceding claims, characterized by , that a second winding end (8) of the spring element (4), in particular facing away from the first winding end (7), is arranged on the gear arrangement (2), in particular on a bearing arrangement (13). [5] Brake booster according to one of claims 3 and 4, characterized by , that the first and / or second winding end (7,8) protrudes radially from the spring element (4), in particular arranged offset from each other by a predetermined angle, preferably oriented at right angles to each other. [6] Brake booster according to any one of the preceding claims, characterized by , that the spring element (4) has a constant and / or rectangular, in particular square, coil cross-section. [7] Brake booster according to claim 6, characterized by, that a width of the coil cross-section in radial extension of the spring element (4) is greater than a height of the coil cross-section in axial extension of the spring element (4), wherein the width and the height in particular have a ratio of at least 3 to 2. [8] Brake booster according to any one of the preceding claims, characterized by , that an outer diameter of the first section (7) in the relaxed state is larger than an outer diameter of the second section (8), wherein the outer diameters in particular have a ratio of at least 3 to 2. [9] Brake booster according to any one of the preceding claims, characterized by , that the number of turns of the second section (8) is greater than the number of turns of the first section (7), wherein in particular the number of turns of the first section (7) is at least two and / or the number of turns of the second section (8) is at least ten. [10] Braking system of a motor vehicle, characterized by a brake booster (1) according to one of the preceding claims. [11] motor vehicle, characterized by a braking system according to claim 10.

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