Electromechanically actuable brake pressure generator

Abstract

The invention relates to an electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, the brake pressure generator having a spindle drive unit (38) for converting a drive-side rotational movement (a) into a translational movement (b) for piston-actuating a hydraulic piston / cylinder unit (34), wherein a transmission unit (22) is arranged between the spindle drive unit (38) and an electric drive motor (18). The drive motor axis (26) and the axis (42) of the spindle drive unit (38) are arranged radially offset from each other, and the piston / cylinder unit (34) and the electric drive motor (18) are arranged on axially opposite sides of the transmission unit (22).

Description

Technical Field

[0001] The invention relates to an electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, the brake pressure generator having a spindle drive unit for converting a drive-side rotational movement into a translational movement for piston-actuating a hydraulic piston / cylinder unit, wherein a transmission unit is arranged between the spindle drive unit and the electric drive motor. The invention also relates to a vehicle comprising such an electromechanically drivable brake pressure generator.

[0002] For future drive concepts of motor vehicles, alternative brake pressure build-up devices are required, since negative pressure is no longer available for operating conventional vacuum brake boosters. For this purpose, electromechanical brake pressure generators of interest have been developed.

[0003] In an electromechanical brake pressure generator of the type of interest here, the braking force on the piston / cylinder unit is generated by means of an electric motor or another suitable electric drive. Such a brake pressure generator can be used not only to provide an auxiliary force but also, in so-called brake-by-wire systems, to generate only the brake actuation force. Electromechanical brake pressure generators are therefore particularly advantageous in autonomous driving. Background Art

[0004] According to the generally known prior art regarding such electromechanical brake force generators, when the brake pedal is actuated, the manually applied pedal travel is measured by an electronic pedal travel sensor and forwarded to an electronic control device. The electronic control device calculates the corresponding control signal for the electric drive motor from this. The motor torque is converted into a boost for the driver via a multi-stage gear transmission. The force provided by the booster is converted into a hydraulic pressure for braking in a hydraulic piston / cylinder unit. The electromechanical brake pressure generator provides a braking feel comparable to a conventional vacuum brake booster. The braking feel can therefore be matched to the brand-specific features of the vehicle by the electronic control unit via software.

[0005] WO 2017 / 045804 A1 discloses an electromechanical brake pressure generator of the type described. The brake pressure generator comprises an electric drive motor, which is operatively connected to a spindle drive unit via a multi-stage spur gear mechanism, so that the rotation of the electric drive motor causes a translational movement of the spindle of the spindle drive unit for actuating the master brake cylinder. However, the multi-stage spur gear mechanism produces a considerable distance in the radial direction relative to the spindle drive unit in the case of a relatively small transmission ratio, so that the entire assembly of the electromechanical brake force generator has a considerable structural failure.

[0006] The object of the present invention is to provide an electromechanically drivable brake pressure generator which is characterized by a space-saving transmission ratio and a cost-effective design for transmitting the electric drive power to the spindle drive unit. Summary of the invention

[0007] The object is achieved by means of an electromechanically drivable brake pressure generator according to the invention for a hydraulic brake system of a vehicle. Advantageous developments of the invention include: the planetary gear mechanism is constructed in two stages; the piston / cylinder unit is accommodated in a valve housing, the electric drive motor is supported relative to the valve housing; the electric drive motor has a motor housing fixed to the valve housing, and the planet carrier is fixed to the motor housing in a rotationally fixed manner; the motor shaft of the electric drive motor is extended into the valve housing, and a rotation speed sensor is arranged in the valve housing at the axial end opposite to the electric drive motor. The invention also proposes a vehicle having a hydraulic brake system including an electromechanical brake pressure generator according to the invention.

[0008] The invention includes the technical teaching that the drive motor axis and the axis of the spindle drive unit are arranged radially offset from one another and that the piston / cylinder unit and the electric drive motor are arranged on axially opposite sides of the transmission unit.

[0009] According to the invention, the axis of the spindle drive unit is arranged parallel to the drive motor axis, but radially adjacent to the drive motor axis. This arrangement provides the structural unit with a higher compactness in the axial direction. Unlike the piston / cylinder unit, which is arranged in the valve housing, for example, the electric drive motor is arranged outside the valve housing. Here, the transmission unit is arranged in the axial direction between the drive motor and the piston / cylinder unit.

[0010] The electric drive motor is provided as an external motor, which therefore does not require space inside the valve housing. As a result, the valve housing can be made smaller, thus saving installation space and material of the valve housing, which is usually made of solid material. As a result, such an electromechanically drivable brake pressure generator can be made smaller and more economical.

[0011] In a preferred embodiment of the invention, the transmission unit has a planetary gear mechanism, which is arranged coaxially with the drive motor axis. The planetary gear mechanism has the advantage that a high transmission ratio can be achieved, while the structural space is reduced due to the high power density. In addition, the planetary gear mechanism has a low noise characteristic. Due to the rotational freedom of the transmission elements: sun gear, planetary gear, planet carrier and ring gear, the planetary gear mechanism provides a large margin in terms of design and transmission ratio.

[0012] In another preferred embodiment of the invention, the planetary gear mechanism has an output-side hollow wheel, which cooperates with the spur gear of the main shaft of the drive spindle drive unit. The hollow wheel preferably has an external toothing, via which the hollow wheel engages with the spur gear. Therefore, no further spur gears are required. The number of components is correspondingly reduced. Such a transmission unit can also be provided more compactly.

[0013] Preferably, the planetary gears of the planetary gear transmission are configured as multi-stage planetary gears. Multi-stage planetary gears are planetary gears that have at least two different toothings with different pitch diameters. Here, the toothings are arranged in a certain section of the multi-stage planetary gear. Here, the multi-stage planetary gear can be configured in one piece or in multiple pieces. Here, the planetary gear transmission with multi-stage planetary gears has the advantage that the number of components can be reduced. In addition, the multi-stage planetary gear provides the following advantage: compared with alternatives with a comparable total transmission ratio, the volume of such a transmission is smaller.

[0014] In an advantageous development, the planetary gear is designed in two stages. A two-stage planetary gear has the advantage that the planet carrier can be designed to be floating, thereby reducing the outlay for the support.

[0015] Advantageously, the piston / cylinder unit is accommodated in the valve housing and the electric drive motor is supported relative to the valve housing. Therefore, due to the support relative to the valve housing, no additional support options have to be provided. Therefore, the electric drive motor and the piston / cylinder unit have the same reference point. As a result, no significant relative movement occurs between the two elements. Therefore, wear in the path between the electric drive motor and the piston / cylinder unit due to relative movement is avoided.

[0016] In another advantageous embodiment, the electric drive motor has a motor housing fixed to the valve housing, to which the planet carrier is fixed in a rotationally fixed manner. The planet carrier is thus fixedly connected to the motor housing. Accordingly, no additional fixing of the planet carrier is necessary. In addition, the motor shaft can be supported relative to the motor housing. Thus, the motor housing fulfills a variety of functions in addition to accommodating the drive motor. By fixing the motor housing to the valve housing, the previously described uniform reference point and the advantages associated therewith can be ensured.

[0017] According to a suitable embodiment, the motor shaft of the electric drive motor is extended into the valve housing, in which a rotation speed sensor is arranged at the axial end opposite the electric drive motor. The rotation speed sensor is preferably applied directly to the printed circuit board. Preferably, the rotation speed sensor is used to detect the signal of the magnetic element on the axial end side of the motor shaft. Thus, the electronic components can be combined and arranged in the area of ​​the electronic control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

[0019] Figure 1 A schematic diagram showing an exemplary embodiment of a drive train of an electromechanical brake pressure generator according to the invention, and Figure 2 A sectional view of an exemplary embodiment of a drive train of an electromechanical brake pressure generator according to the invention is shown. DETAILED DESCRIPTION

[0020] exist Figure 1 1 shows a schematic diagram of an embodiment of a drive train 14 of an electromechanical brake pressure generator according to the invention. The drive train 14 comprises an electric drive motor 18, by which a rotational movement a can be generated. The electric drive motor 18 is mechanically connected to a transmission unit 22. The transmission unit 22 is a planetary gear mechanism in this embodiment. The planetary gear mechanism 22 is positioned coaxially with the drive motor axis 26 and is arranged on a valve housing 28 of the brake pressure generator.

[0021] The driving speed of the electric drive motor 18 is converted into a slower speed by the planetary gear mechanism 22. The planetary gear mechanism 22 is mechanically connected to the hydraulic module 30 on the output side. The hydraulic module 30 has a piston / cylinder unit 34, which generates a brake pressure by an axial translational movement b of a spindle drive unit 38. The drive train 14 shown in this embodiment is arranged biaxially. This means that the axis 42 of the spindle drive unit 38 of the hydraulic module 30 is arranged parallel to the drive motor axis 26 and radially offset therefrom.

[0022] Here, the electric drive motor 18 is not arranged in the valve housing 28, but rests externally on the planetary gear mechanism 22. The electric drive motor 18 and the piston / cylinder unit 34 arranged in the valve housing 28 are therefore positioned on axially opposite sides of the transmission unit 22. As a result, space for accommodating the electric drive motor 18 is saved in the valve housing 28, so that the valve housing 28 can be designed to be smaller.

[0023] Figure 2 1 shows a cross-sectional view of an embodiment of a drive train 14 of an electromechanical brake pressure generator according to the invention. Figure 1 The drive train 14 is shown. In this exemplary embodiment, the hydraulic module 30, the electric drive motor 18 and the planetary gear 22 are arranged in a common outer housing 46, which is connected to the valve housing 28 via a fastening device 50. The electric drive motor 18 is additionally arranged in the outer housing 46 in a separate motor housing 54, which is also connected to the valve housing 28.

[0024] The electric drive motor 18 has a motor shaft 58, which is supported relative to the motor housing 54 via a bearing 62. A sun gear 66 of the planetary gear 22 is arranged on the motor shaft 58 and is driven by the electric drive motor 18. The sun gear 66 cooperates with planetary gears 70, which can be rotated via a planet carrier 72 fixed to the motor housing 54.

[0025] In this embodiment, the planetary gear 70 is configured as a multi-stage planetary gear. This means that the planetary gear 70 has a larger diameter in the engagement region with the sun gear 66 than in the engagement region with the hollow gear 74. Here, the hollow gear 74 is rotatably supported relative to the valve housing 28. The motor shaft 58 extends into the valve housing 28 through the planetary gear mechanism 22. At the axial end of the motor shaft 58 opposite the electric drive motor 18, a rotation speed sensor 78 is arranged in the valve housing 28, which detects the rotation speed of the motor shaft 58. In this embodiment, the rotation speed is detected by a magnetic element 80 at the axial end of the motor shaft 58.

[0026] The hollow gear 74 has an outer toothing, by means of which the hollow gear 74 cooperates with a spur gear 82 of the spindle drive unit 38, so that the spur gear 82 is set in rotation. The spindle drive unit 38 comprises a spindle 86, which is rotatably held in a spindle drive receptacle 90 that is fixedly connected to the valve housing 28. A spindle nut 94 is additionally accommodated in the spindle drive receptacle 90, which engages with the spindle 86, so that the spindle nut 94 can be axially displaced as the spindle 86 rotates.

[0027] Spur gear 82 is fixedly connected to a cup-shaped structural element 98, which is rotatably mounted relative to spindle drive receptacle 90. Structural element 98 is additionally fixedly connected to the end of spindle 86, so that spindle 86 rotates with spur gear 82 via structural element 98.

Claims

1. An electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, the brake pressure generator having a spindle drive unit (38) for converting a drive-side rotational movement (a) into a translational movement (b) for piston-actuating a hydraulic piston / cylinder unit (34), wherein: A transmission unit (22) is arranged between the spindle drive unit (38) and the electric drive motor (18), characterized in that the drive motor axis (26) and the axis (42) of the spindle drive unit (38) are arranged radially offset from each other, and the piston / cylinder unit (34) and the electric drive motor (18) are arranged on axially opposite sides of the transmission unit (22), wherein the transmission unit (22) has a planetary gear mechanism, which is arranged coaxially with the drive motor axis (26), and wherein the planetary gear mechanism has an output-side hollow wheel (74) that interacts with a spur gear (82) of a spindle (86) driving the spindle drive unit (38).

2. An electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, the brake pressure generator having a spindle drive unit (38) for converting a drive-side rotational movement (a) into a translational movement (b) for piston-actuating a hydraulic piston / cylinder unit (34), wherein: A transmission unit (22) is arranged between the spindle drive unit (38) and the electric drive motor (18), characterized in that the drive motor axis (26) and the axis (42) of the spindle drive unit (38) are arranged radially offset from each other, and the piston / cylinder unit (34) and the electric drive motor (18) are arranged on axially opposite sides of the transmission unit (22), wherein the transmission unit (22) has a planetary gear mechanism, which is arranged coaxially with the drive motor axis (26), and wherein the planetary gears (70) of the planetary gear mechanism are constructed as multi-stage planetary gears.

3. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that: The planetary gear train is designed in two stages.

4. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that: The piston / cylinder unit (34) is accommodated in a valve housing (28) and the electric drive motor (18) is mounted relative to the valve housing.

5. The electromechanically drivable brake pressure generator according to claim 4, characterized in that The electric drive motor (18) has a motor housing (54) which is fixed to the valve housing (28) and to which a planet carrier (72) is fixed in a rotationally fixed manner.

6. The electromechanically drivable brake pressure generator according to claim 4, characterized in that A motor shaft (58) of the electric drive motor (18) extends into the valve housing (28), in which a rotational speed sensor (78) is arranged at an axial end opposite the electric drive motor (18).

7. A vehicle comprising an electromechanical brake pressure generator for a hydraulic brake system according to any of the preceding claims.

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