Electromechanical brake pressure generator with spindle drive unit and brake system

Abstract

The invention relates to an electromechanical brake pressure generator (1) having a main shaft transmission unit (2) for converting a rotational movement of an electrically driven drive shaft (3) into a translational movement of a piston (4) coupled to the main shaft transmission unit (2), wherein the main shaft transmission unit (2) is in operative connection with the drive shaft (3) via a multi-stage transmission (5). According to the invention, the multi-stage transmission (5) is a planetary gear transmission having a first stage and a second stage (5.1, 5.2). A main shaft (6) or a main shaft nut (7) of the main shaft transmission unit (2) is drivable by means of the transmission (5) and is rotatably supported in a housing (9) of the brake pressure generator (1) by a bearing assembly (8) which is subjected to axial and radial forces. The invention also relates to a brake system for a vehicle having an electromechanical brake pressure generator (1) according to the invention.

Description

TECHNICAL FIELD

[0001] The invention relates to an electromechanical brake pressure generator with a spindle drive unit. The spindle drive unit serves to convert the rotational movement of a drive shaft, which is driven in the manner of an electric motor, into a translational movement of a piston coupled to the spindle drive unit.

[0002] The described electromechanical brake pressure generator should not only be used to provide a brake assist force, but also to generate a brake force independently in so-called "brake-by-wire" systems. In this design variant, it can be used, inter alia, to generate a brake force or brake pressure in a vehicle that drives autonomously.

[0003] Therefore, a brake system for a vehicle is also proposed, which comprises an electromechanical brake pressure generator according to the invention. BACKGROUND

[0004] In the electromechanical brake pressure generator, the drive shaft can be arranged axially parallel or coaxially to the spindle drive unit or to the piston. The invention first relates to an electromechanical brake pressure generator in which the drive shaft is arranged coaxially. Such a brake pressure generator is known, for example, from WO 2017 / 045804 A1. SUMMARY

[0005] Starting from the above-mentioned prior art, it is the task of the invention to specify an optimized design for an electromechanical brake pressure generator. In particular, the bearing structure of the spindle drive unit should be improved while making full use of the available installation space.

[0006] To solve this task, an electromechanical brake pressure generator is specified, which has a spindle drive unit for converting the rotational movement of a drive shaft driven in the manner of an electric motor into a translational movement of a piston coupled to the spindle drive unit, wherein the spindle drive unit is connected via a multi-stage transmission mechanism with the drive shaft, wherein the multi-stage transmission mechanism is a planetary gear transmission mechanism having a first stage and a second stage, and the spindle or spindle nut of the spindle drive unit can be driven by means of the transmission mechanism, which is rotatably supported in the housing of the brake pressure generator by a bearing assembly that takes up axial and radial forces, wherein the bearing assembly has a pot-shaped inner ring which is configured in one piece or in multiple pieces, which has a pot bottom for connecting, on the one hand, to the spindle or the spindle nut and, on the other hand, to the transmission mechanism by means of a pin. Advantageous refinements of the invention can be gathered from the following: The bearing assembly comprises axial needle bearings for taking up axial forces and radial slide bearings for taking up radial forces; the bearing assembly comprises radial thrust ball bearings for taking up axial and radial forces; the bearing assembly is completely accommodated in the housing and / or is fixed in the housing by means of an outer ring of the bearing assembly; the bearing assembly surrounds the spindle and / or the spindle nut; the spindle is made of metal and / or the spindle nut is made of plastic; the bearing assembly is supported on the housing in the axial direction by means of a plastic ring; the bearing assembly comprises a clamping ring which holds the bearing assembly together and / or constitutes a slide bearing; the bearing assembly is fixed in the housing by means of a caulking or a screw connection of the outer ring in the housing; the spindle is made of steel or aluminum; the inner ring of the bearing assembly is supported on the housing in the axial direction by means of a plastic ring. Furthermore, a brake system for a vehicle is specified, which has an electromechanical brake pressure generator according to the invention.

[0007] The proposed electromechanical brake pressure generator has a spindle drive unit for converting the rotational movement of a drive shaft driven in the manner of an electric motor into a translational movement of a piston coupled to the spindle drive unit. The spindle drive unit is here connected via a multi-stage transmission mechanism with the drive shaft. According to the invention, the multi-stage transmission mechanism is a planetary gear transmission mechanism having a first stage and a second stage. By means of the transmission mechanism, the spindle or spindle nut of the spindle drive unit can be driven, which is rotatably supported in the housing of the brake pressure generator by a bearing assembly that takes up axial and radial forces.

[0008] The use of a multi-stage transmission in the form of a planetary gear mechanism proves to be advantageous, in particular in the case of a coaxial arrangement of the drive shaft and the spindle drive unit, since in this case a brake pressure generator is achieved which is very compact at least in the radial direction. In the axial direction, the space requirement can be slightly increased due to the plurality of stages of the planetary gear mechanism. This is prevented here, however, by a compact bearing assembly for rotatably supporting the spindle or the spindle nut. Since the bearing assembly can withstand not only axial forces but also radial forces.

[0009] At the same time, a high transmission ratio can be achieved with the aid of the multi-stage planetary gear mechanism.

[0010] According to a first preferred embodiment of the application, the bearing assembly comprises an axial needle bearing for withstanding axial forces and a radial plain bearing for withstanding radial forces. In this way, a bearing assembly which is small in construction in the axial and radial directions can be realized. Since needles are used as rolling bodies, the axial construction height is reduced. The construction of a plain bearing without rolling bodies essentially does not require additional space.

[0011] According to a further preferred embodiment of the application, the bearing assembly comprises a radial thrust ball bearing (Schrägkugellager) for withstanding axial forces and radial forces. The radial thrust ball bearing combines an axial bearing and a radial bearing in one single bearing, so that this embodiment is also very space-saving.

[0012] Preferably, the bearing assembly is accommodated completely in the housing or sunk into the housing, so that the bearing assembly does not require additional space. Furthermore, it is preferred that the bearing assembly is integrated into the housing in such a way that hitherto unused space is utilized. Here, for example, regions can be involved which are delimited in the axial direction on the one hand by the planetary gear mechanism and on the other hand by a housing wall which separates the bearing assembly from the main brake cylinder integrated into the housing. In the radial interior, this region can be delimited by the torque support of the spindle nut or of the spindle. In the radial exterior, current lines and / or signal lines leading to the electric motor or to sensors can form a limitation.

[0013] Furthermore, it is proposed that the bearing assembly is fixed in the housing by means of an outer ring of the bearing assembly, for example by means of a caulking (Verstemmen) or a screw connection of the outer ring in the housing. In the case of caulking, the cutting of an outer thread on the outer ring can be dispensed with, so that this solution can be realized particularly simply and cost-advantageously. A screw connection has the advantage that it can be loosened without damage, if necessary.

[0014] Furthermore, the bearing assembly preferably surrounds the spindle and / or the spindle nut. That is to say, the bearing assembly does not lead to an increase in the overall structural length of the brake pressure generator. This is predetermined only by the structural length of the spindle drive unit, the planetary gear and the drive shaft. Thus, in the axial direction, no bearing assembly is formed.

[0015] The spindle is preferably made of metal, in particular steel or aluminum, since it is subjected to high loads and metal materials have a high strength.

[0016] In contrast thereto, the spindle nut can be made of plastic, so that it can be produced cost- advantageously.

[0017] In an improvement of the application, it is proposed that the bearing assembly has a pot-shaped inner ring which is configured in one piece or in multiple pieces, which has a pot bottom on the one hand for the connection to the spindle or the spindle nut and on the other hand for the connection to the transmission. The pot shape of the inner ring facilitates the arrangement of the bearing assembly in the height of the spindle or the spindle nut, since it continues in a curvature in the direction of the piston which is coupled at the other end to the spindle drive unit. Furthermore, the region of the curvature can be used to form a bearing, so that the rolling bodies together with the outer ring do not protrude in the axial direction beyond the pot bottom.

[0018] For the connection to the spindle or the spindle nut, depending on which component is driven via the drive shaft, the pot bottom can have a central opening in which the spindle or the spindle nut section-wise is accommodated. The connection to the transmission or the planetary gear can be realized for example by a pin. Thus, the pot bottom is at the same time a planet carrier.

[0019] The multiple-piece embodiment of the inner ring of the bearing assembly has the advantage that on the one hand the manufacture of the individual components is simplified and on the other hand the best material for the respective function of the component is chosen. The component of the inner ring which constitutes the contact surface for the rolling bodies must in principle be made of a hardenable material, since the rolling bodies require a hard and wear-resistant contact surface. Thus, the material can be in particular a carbon-containing material. Since in the material hardening a distortion of the component can result, so that a costly reworking of the component is necessary if necessary, in particular in the region of the openings / holes in the pot bottom, a further material is provided for the construction of the pot bottom, which in particular does not have to be subjected to a hardening process.

[0020] Furthermore, it is proposed that the bearing assembly, preferably the inner ring of the bearing assembly, is supported in the axial direction on the housing by means of a plastic ring. The plastic ring constitutes a plain bearing for the case that the component of the spindle drive unit which is driven by means of the drive shaft, that is to say the spindle or the spindle nut, is pulled in the axial direction.

[0021] Ideally, the bearing assembly constitutes a preassembled structural unit which is inserted as a unit. In this way, the assembly of the brake pressure generator can be simplified. Furthermore, the bearing assembly can already be filled with lubricating grease. In the improvement of the application, it is therefore also proposed that the bearing assembly comprises a clamping ring which holds the bearing assembly together. Thus, by means of the clamping ring, the bearing assembly can be preassembled and inserted as a preassembled unit into the housing of the brake pressure generator. Alternatively or additionally, the clamping ring can constitute the plain bearing.

[0022] Since the preferred field of application of the brake pressure generator according to the application is a vehicle, it is furthermore proposed that a brake system for a vehicle comprises an electromechanical brake pressure generator according to the application. The advantages of the brake pressure generator according to the application, in particular the small space requirement or small structural length, are particularly evident in a vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0023] In the following, preferred embodiments of the application are explained in detail with the aid of the drawings. These show:

[0024] Figure 1 a longitudinal section of a first electromechanical brake pressure generator according to the application with a spindle drive unit and a bearing assembly comprising an axial needle bearing and a radial plain bearing,

[0025] Fig. 2 shows Figure 1 an enlarged detail of a) an outer ring with a caulking and a one-piece inner ring and b) an outer ring with a threaded connection and a multi-piece inner ring,

[0026] Fig. 3 shows a similar detail to Fig. 2, but with a bearing assembly configured as a radial thrust ball bearing, wherein a) has a one-piece inner ring and b) has a multi-piece inner ring with a cage,

[0027] Figure 4 a similar detail to Figure 3b ), but with a modified outer ring and inner ring. DETAILED DESCRIPTION

[0028] In Figure 1 the electromechanical brake pressure generator 1 shown in Fig. 1 comprises a housing 9 in which a spindle drive unit 2 coupled with a piston 4 is accommodated. The spindle drive unit 2 comprises a spindle 6 which is rotatably supported in the housing 9 by means of a bearing assembly 8. On the spindle 6, a spindle nut 7 is arranged and fixed against a torsion by means of a torque support 16. Upon rotational movement of the spindle 6, the spindle nut 7 is moved in axial direction and here drives the piston 4 such that this is inserted deeper into a cylindrical pressure chamber 17 configured in the housing 9.

[0029] The main shaft 6 is driven by the drive shaft 3, which is connected to the main shaft 6 via a multi-stage transmission 5 in the form of a planetary transmission. The transmission 5 here comprises a first stage 5.1 and a second stage 5.2. The second stage 5.2 comprises planets, which are supported by means of pins 13. The pins 13 in turn are connected to a pot-shaped inner ring 11 of the bearing assembly 8, which is fitted onto the main shaft 6.

[0030] The pot shape of the inner ring 11 makes it possible for the bearing assembly 8 to be arranged at the height of the main shaft transmission unit 2, so that the bearing assembly 8 is not additionally constructed in the axial direction. In this way, the construction length of the brake pressure generator 1 can be kept small. Furthermore, the construction space available in the housing 9 is used (see dotted line), which is limited upwards by the second stage 5.2 of the transmission 5, downwards by the housing wall for separating the bearing assembly 8 from the brake cylinder 18, radially inwards by the torque support 16 and radially outwards by the current lines and / or signal lines 19.

[0031] As can be gathered from the enlarged view of Figure 2, Figure 1 The bearing assembly 8 of the brake pressure generator 1 comprises an axial needle bearing 8.1 and a radial plain bearing 8.2. The axial needle bearing 8.1 has needle-shaped rolling bodies 20, which are constructed only slightly in the axial direction. The radial plain bearing 8.2 is realized on the left-hand side, i.e. on the Figure 2a ) side, by means of the contact between the outer ring 10 and the inner ring 11 and on the right-hand side, i.e. on the Figure 2b ) side, by means of a plastic ring, which is inserted into the outer ring 10 of the axial needle bearing 8.1.

[0032] Furthermore, in Figure 2a ) the outer ring 10 is fixed in the housing 9 by means of a caulking 21. In Figure 2b ) the fixing is realized by means of a screw connection 22.

[0033] In Figure 2a ) the inner ring 11 is constructed in one piece and in Figure 2b ) in multiple pieces.

[0034] For the case in which the main shaft 6 should be pulled in the axial direction in operation, both figures have in common the plastic ring 14, via which the bearing assembly 8 is supported in the axial direction.

[0035] The one- or multi-part pot-shaped inner ring 11 of the bearing assembly 8 has a pot bottom 12 with a central recess 23 into which the main shaft 6 is inserted. For a torsionally rigid connection, the pot bottom 12 can be welded to the main shaft 6. Alternatively, the recess 23 in the pot bottom 12 and the main shaft 6 can have corresponding, non-rotationally symmetrical contours 24, 25. Furthermore, the pot bottom 12 has holes 26 into which the pins 13 are pressed.

[0036] In Figure 3a ) and 3b) other preferred embodiments are shown. Both embodiments have in common that here the bearing assembly 8 is formed by a radial thrust ball bearing 8.3 with spherical rolling bodies 20. These rolling bodies can be guided by a cage 27 (as shown exemplary in Figure 3b ). If the cage 27 is dispensed with, the number of rolling bodies 20 can be increased for an increased load capacity. The outer ring 10 is respectively shrunk in the housing 9. The inner ring 11 is one-part in Figure 3a ) and multi-part in Figure 3b ).

[0037] In Figure 3a ) and Figure 3b ) the radial thrust ball bearing 8.3 has in addition a clamping ring 15 which holds the inner ring 11 and the outer ring 10 together. Thus, the radial thrust ball bearing 8.3 can be preassembled and inserted as a preassembled unit into the housing 9 of the brake pressure generator 1. Here, the clamping ring 15 is two-part in order to at the same time constitute a plain bearing.

[0038] In Figure 4 ) another embodiment is shown. This embodiment differs from the embodiment of Figure 3b ) in particular in that the inner ring 11 comprises more than two parts, namely three parts. The first part constitutes the pot bottom 12, the other part constitutes the actual inner ring 11 with the contact faces for the rolling bodies 20. The third part connects the two parts. Each part can thus be made of a suitable material according to its function. At the same time, each part has a relatively simple shape, which simplifies the manufacture of the inner ring 11.

Claims

1. Electromechanical brake pressure generator (1) having a spindle drive unit (2) for converting the rotational movement of a drive shaft (3) driven in the manner of an electric motor into a translational movement of a piston (4) coupled to the spindle drive unit (2), wherein The spindle drive unit (2) is connected via a multi-stage transmission (5) to the drive shaft (3), characterized in that the multi-stage transmission (5) is a planetary gear transmission with a first stage (5.1) and a second stage (5.2) and the spindle (6) or spindle nut (7) of the spindle drive unit (2), which is rotatably supported in the housing (9) of the brake pressure generator (1) by a bearing assembly (8) that bears axial and radial forces, can be driven by means of the transmission (5), wherein the bearing assembly (8) has a one- or multi-part pot-shaped inner ring (11) with a pot bottom (12) for connection to the spindle (6) or spindle nut (7) on the one hand and to the transmission (5) by means of a pin (13) on the other hand.

2. Brake pressure generator (1) according to claim 1, characterized in that The bearing assembly (8) comprises axial needle bearings (8.1) for bearing axial forces and radial slide bearings (8.2) for bearing radial forces.

3. Brake pressure generator (1) according to claim 1, characterized in that The bearing assembly (8) comprises radial thrust ball bearings (8.3) for bearing axial and radial forces.

4. Brake pressure generator (1) according to any of the preceding claims 1 to 3, characterized in that The bearing assembly (8) is completely accommodated in the housing (9) and / or is fixed in the housing (9) by means of an outer ring (10) of the bearing assembly (8).

5. Brake pressure generator (1) according to any of the preceding claims 1 to 3, characterized in that The bearing assembly (8) surrounds the spindle (6) and / or the spindle nut (7).

6. Brake pressure generator (1) according to any of the preceding claims 1 to 3, characterized in that The spindle (6) is made of metal and / or the spindle nut (7) is made of plastic.

7. Brake pressure generator (1) according to any of the preceding claims 1 to 3, characterized in that The bearing assembly (8) is supported on the housing (9) in the axial direction by means of a plastic ring (14).

8. Brake pressure generator (1) according to any of the preceding claims 1 to 3, characterized in that The bearing assembly (8) comprises a clamping ring (15) that holds the bearing assembly (8) together and / or constitutes a slide bearing.

9. Brake pressure generator (1) according to claim 4, characterized in that The bearing assembly (8) is fixed in the housing (9) by means of a caulking or a screw connection of the outer ring (10) in the housing (9).

10. Brake pressure generator (1) according to claim 6, characterized in that The spindle (6) is made of steel or aluminum.

11. Brake pressure generator (1) according to claim 7, characterized in that The inner ring (11) of the bearing assembly (8) is supported on the housing (9) in the axial direction by means of a plastic ring (14).

12. Brake system for a vehicle, comprising an electromechanical brake pressure generator (1) according to any of the preceding claims 1 to 11.

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