Compact simulator unit for a hydraulic brake device

Abstract

The invention relates to a hydraulic simulator unit (1) for generating a counterforce (G), which acts counter to an actuating force (B), for a brake device (100) of a hydraulic vehicle brake system, comprising at least one piston (7) which is accommodated in a simulator chamber (4) and can be moved out of an unactuated starting position by hydraulic loading and, during the movement, acts on at least one spring element (9). In order to make the operation of the simulator unit (1) low-noise and low-wear, to reduce overall length and to simplify assembly, the invention proposes that the spring element (9) at least partly surrounds the piston (7) radially on the outside.

Description

[0001] Compact simulator unit for a hydraulic brake device

[0002] The invention relates to a simulator unit according to the preamble of claim 1 for a brake device for a hydraulic motor vehicle brake system, in particular a hydraulic brake-by-wire motor vehicle brake system, and a corresponding brake device.

[0003] Modern vehicles increasingly utilize electronically controlled braking systems, particularly so-called brake-by-wire systems. These systems offer several advantages over conventional braking systems. For example, braking can be performed completely independently of the driver when needed and flexibly adapted to the specific driving situation. The required installation space is reduced compared to a conventional braking system, and it can also be positioned more flexibly within the vehicle. In their regular braking mode, modern brake-by-wire systems are indirectly and electronically controlled by the driver through sensor-based detection of a braking request, thus operating completely independently of the driver. To generate the necessary system pressure in this regular braking mode, a driver-independent pressure generator is used, which is usually driven by an electric motor.

[0004] In conventional braking systems, the pressure from the hydraulic circuit exerts a reaction force back into the driver's pedal when the brake pedal is pressed. This force varies depending on the braking scenario, vehicle load, and road conditions. However, in brake-by-wire systems, such feedback from the wheel brake cylinder to the brake pedal is prevented in regular, externally actuated operation by disconnecting a direct hydraulic connection. Therefore, it is necessary to provide the driver with a familiar and comfortable pedal feel despite the lack of direct feedback.

[0005] For this purpose, it is known to simulate the feedback using a separate simulator unit. Here, the simulator unit generates a counterforce opposing the actuating force with a defined displacement- or stroke-dependent curve, which is also referred to as the characteristic curve of the simulator unit. The aim is for the characteristic curve of the simulator unit to be as similar as possible to a real feedback system, such as that found in a conventional driver-operated braking system.

[0006] A well-known and widely used design of a simulator unit is known, for example, from DE 102020216514 A1. This design comprises, in a series circuit, a hydraulically actuated piston, a steel compression spring with a linear characteristic, an intermediate piston, and an elastomeric compression spring with a progressive characteristic. The steel compression spring is inserted or clamped between the piston and the intermediate piston and ensures an axial distance between the two components in the unactuated starting position. During regular braking operation, the simulator unit is hydraulically connected to a pressure chamber of a pedal-actuated master cylinder unit. When the master cylinder unit is actuated, the piston is pushed from its starting position towards the intermediate piston, thereby compressing the steel compression spring. Simultaneously, the intermediate piston is pressed against the elastomeric compression spring by the force exerted by the steel compression spring.Once the axial distance between the piston and the intermediate piston is exhausted, the piston enters a direct mechanical connection with the intermediate piston and is moved simultaneously with it during the further stroke.

[0007] After the hydraulic actuation force is removed, the pistons are returned to their unactuated starting position by the built-up spring tension.

[0008] The following aspects of the aforementioned structural concept can be considered in need of improvement:

[0009] The intermediate piston, being a massive component, is quite heavy and inherently prone to tilting. This tilting can lead to noise and increased wear during operation. To counteract this problem, the intermediate piston must be manufactured with exceptional precision using complex processes and tight tolerances, which increases costs. The simulator unit has a significant overall length. During assembly, numerous individual components must be handled and, in some cases, secured and held separately, particularly the steel compression spring.

[0010] The object of the invention is therefore to propose an improved simulator unit which avoids or reduces the disadvantages of the known prior art.

[0011] The problem is solved according to the invention by a simulator unit with the combination of features according to claim 1. Dependent claims specify further advantageous embodiments and developments of the invention.

[0012] The invention provides that the spring element surrounds the piston radially on the outside, at least in sections.

[0013] An intermediate piston can be omitted, and the overall length and assembly effort can be significantly reduced.

[0014] In addition to reducing the number of parts, the assembly of the spring element is particularly simple. The spring element can be inserted separately into the cavity in the housing before the piston is installed, where it remains in the correct position on its own and does not need to be held or aligned separately.

[0015] Due to its positioning according to the invention, the spring element is located in the wet area of ​​the simulator chamber and is surrounded by the hydraulic pressure medium. The significantly higher viscosity of the pressure medium compared to air has a vibration-damping effect on the spring element, thereby reducing noise. For example, spring whizzing and unwanted impacts against surrounding components are reduced. The pressure medium also protects the spring element from corrosion.

[0016] Furthermore, the invention claims a braking device with at least one simulator unit according to the invention. Further features and advantages of the invention will become apparent from the following description. The following were shown:

[0017] Fig. 1 shows an exemplary braking device in a highly simplified internal structure view.

[0018] Fig. 2 Axial section of a first embodiment of the simulator unit in an unactuated initial state.

[0019] Fig. 3 shows a closure lid according to the design shown in Fig. 2.

[0020] Fig. 4 A piston according to the design shown in Fig. 2.

[0021] Fig. 5 Axial section of a second embodiment of the simulator unit in an unactuated initial state.

[0022] Fig. 6 shows a closure lid according to the design shown in Fig. 5.

[0023] Fig. 7 Adjustment of the axial distance by using different closure lid thicknesses.

[0024] Fig. 1

[0025] Fig. 1 shows an example of a brake-by-wire braking device 100 for a hydraulic braking system of a motor vehicle.

[0026] To initiate braking, the driver operates a brake pedal (not shown here) which actuates a piston rod 13 coupled to it, which transmits the driver's actuation force B to a master cylinder unit 10.

[0027] In a regular braking mode, this actuation is detected and processed electronically via a sensor device (not shown here), whereupon an electrically driven pressure generation device (also not shown here) provides the required braking pressure.

[0028] A pressure chamber 11 filled with a hydraulic pressure medium, for example brake fluid, is arranged in the main cylinder unit 10. In the regular braking mode described above, the pressure chamber 11 is hydraulically connected to a simulator unit 1, which is arranged in or on the housing 101 of the brake device 100, instead of to one or more wheel brakes.

[0029] A container 8 stores the hydraulic pressure medium and serves to supply the brake device 100 with it.

[0030] The simulator unit 1 comprises a simulator chamber 4, which in the embodiment shown is limited by a cavity 3 in the housing 101 and a closure cap 5 connected to the housing 101.

[0031] In the simulator chamber 4 there is a spring element 9 with a linear spring characteristic, a piston 7 and at an axial distance to this an elastomer element 2 with a progressive spring characteristic.

[0032] A piston-side end surface 12 of the closure cover 5 acts as the rear stop for the piston 7 and thus defines its unactuated starting position.

[0033] The spring element 9 is designed as a compression helical spring and is clamped between the piston 7 and the housing 101. The spring element 9 is arranged concentrically to the piston 7 and has a diameter large enough to radially surround the piston 7. With respect to the piston 7, the spring element 9 and the elastomer element 2 are arranged in parallel.

[0034] When the main cylinder unit 10 is actuated, the hydraulic pressure medium from the pressure chamber 11 is displaced into the simulator unit 1 via a connecting channel 19 which can be shut off by means of a shut-off valve 22 and acts on the piston 7 therein. The piston 7 is thereby moved axially towards the elastomer member 2 against the spring force of the spring element 9, thereby pre-tensioning the spring element 9.

[0035] If the design of a specific simulator unit 1 requires an axial distance L (see Fig. 2) between the piston 7 and the elastomer element 2 in the initial position, the piston 7 acts against the spring element 9 alone in this first actuation or stroke section, and the simulator unit 1 exhibits a linear overall characteristic curve. Only when the axial distance L is exhausted is the piston 7 additionally pressed against the elastomer element 2, causing it to be compressed between the piston 7 and the bottom of the cavity 3 and elastically deformed, thereby exerting a reaction force on the piston 7. In this second actuation or stroke section, the characteristic curves of the spring element 9 and the elastomer element 2 superimpose, so that the simulator unit 1 exhibits a progressive overall characteristic curve.

[0036] A sealing sleeve 21 sliding on the outer surface of the piston 7 separates the simulator chamber 4 into a wet area at the side of the opening of the connecting channel 19 from a dry area at the side of the elastomer element 2.

[0037] The total resistance acting against the piston 7 in the simulator unit 1 during the actuation process is perceived by the driver as a counterforce G acting against the actuation force B, the magnitude of which changes characteristically along the actuation path or piston stroke depending on the design and construction of the simulator unit 1.

[0038] Fig. 2

[0039] Fig. 2 shows an exemplary first embodiment of the simulator unit 1 according to the invention in an unactuated starting position in longitudinal section.

[0040] The simulator chamber 4 is limited by the cavity 3 formed in the housing 101 and the closure cover 5.

[0041] The cavity 3 is designed as a type of stepped blind hole bore with a wider section 26 at the mouth and a narrower section 27 at the bottom of the bore, and a radial step 14 in between. The elastomeric element 2 is positioned in the narrower section 27 of the cavity 3 so that it is axially supported against the bottom of the bore 6.

[0042] The piston 7 is formed with a piston base 17 oriented towards the elastomer element 2, a shaft 23, and a collar 15 arranged at the end of the shaft 23. The shaft 23 of the piston 3 extends into the narrower section of the cavity 3 and is hydraulically sealed therein by a sealing sleeve 21 sliding on its surface. The collar 15 serves to guide and radially support the piston 3 on the outer surface of the wider section 27 of the cavity 3 and simultaneously acts as an axial abutment for the spring element 9.

[0043] The spring element 9, made of spring steel, functions as a compression spring and is designed as a helical spring, which is wound radially around the piston 7 or surrounds it radially. The spring element 9 is received in the wider section 26 of the cavity 3 and is axially clamped between the collar 15 of the piston and the radial step 14 of the cavity 3.

[0044] The closure cover 5 is hydraulically sealed to the housing 10, and in the illustrated embodiment is riveted in place. Other joining methods, for example by means of a screw connection secured as desired, remain permissible within the scope of the invention.

[0045] In addition to its sealing function, the sealing cap 5 also serves as a stop for the piston 7 in its rear end position or unactuated starting position, as shown here. The piston 7 is pressed against a piston-side end surface 12 of the sealing cap 5 by the spring element 9.

[0046] The connecting channel 19, which connects the simulator chamber 4 with the pressure chamber 11 of the main cylinder unit 10, opens radially into the simulator chamber 4 at an axial end region of the cavity 3 adjacent to the sealing cover 5. Separate radial channels 16 are provided to ensure that the side of the piston 7 facing away from the elastomer element 2, particularly in the initial position when the piston 7 rests against the sealing cover, is reliably supplied with hydraulic pressure medium. These channels allow for the unimpeded transfer of the hydraulic pressure medium from a radially distal region of the simulator chamber 4, where the connecting channel 19 opens, to the radially proximal region of the simulator chamber 4 and thus to the radial center of the piston 7.

[0047] A drainage channel 20, opening into the narrow section 27 of the cavity 3 near the elastomeric element 2, serves to vent, equalize pressure, and remove the hydraulic fluid, which could potentially bypass the sealing sleeve 21 and enter the dry section of the simulator chamber 4 surrounding the elastomeric element 2. This measure is necessary to prevent any unwanted, unexpected, or unforeseen pneumatic or hydraulic effects from acting on the piston 7 during its actuation or displacement towards the elastomeric element 2.

[0048] Depending on the design of the simulator unit 1, it may be necessary for a defined axial distance L to exist between the piston 7 and the elastomer element 2 in the unactuated starting position, for example, to achieve a linear overall characteristic curve in a first stroke section. Such an axial distance L can be set by a defined axial positioning of the end face 12 of the sealing cap 5, for example, by a defined penetration depth of the sealing cap 5 into the housing 101 or by a separately adjusted axial height S of the sealing cap 5. Reference is also made to Fig. 7 and the associated description.

[0049] In the illustrated embodiment, the piston 7 is designed as a thin-walled, deep-drawn part. The piston 7 has a knob-like projection 18 on its base 17, or rather on its end face facing the elastomer element. When the piston 7 runs onto the elastomer element 2 during actuation, the projection 18 initially causes only a slight deformation of the elastomer element 2. This results in a less abrupt, smoother transition between the linear characteristic curve of the spring element 9 and the progressive characteristic curve of the elastomer element 2. This effect can be used to model the overall characteristic curve of the simulator unit 1.

[0050] Within the invention, the piston base can also be designed differently depending on the specific requirements, for example with several knob-like protrusions 18, flat, domed and the like.

[0051] Figs. 3 and 4

[0052] Figures 3 and 4 show the closure cover 5 and the corresponding piston 7 according to the embodiment shown in Figure 2. For crimping in the housing 101, the closure cover 5 has a separate guide surface 24 and a subsequent cutting edge 25. The guide surface 24 is adapted to the diameter of the corresponding interface in the housing 101 and serves for radial guidance and to prevent the closure cover 5 from tilting within it. The cutting edge 25 has a slightly larger diameter and, when pressed into the housing 101, serves to scrape the housing material from the wall of the interface and plastically displace it into a radial groove arranged between the guide surface 24 and the cutting edge 25, thereby creating a hydraulically tight, permanent connection without additional sealing elements. See also Figure 7.

[0053] The flat end surface 12 of the closure cover 5, which serves as a stop surface for the piston 7, extends over the entire cross-section. The radial channels 16 are designed as radial recesses in a circumferential collar on the piston 7 that is angled axially backwards from the flange 15.

[0054] Figs. 5 and 6

[0055] Fig. 5 shows another embodiment of the simulator unit 1. Unlike the embodiment according to Fig. 2, the piston 7 is not designed as a thin-walled deep-drawn part, but as a solid component made of metal or plastic. To reduce weight, it is provided with a recess on the back.

[0056] The radial collar 15 has a flat end on its rear side; the radial channels 16 are formed in the closure cover 5, see also Fig. 6. In contrast to the embodiment according to Fig. 3, the end surface 12, which serves as a piston stop, is not continuous but is formed on an axially projecting ring, which is perforated by several recesses or radial channels 16.

[0057] Furthermore, in the illustrated embodiment, the axial distance L is zero, which means that the piston 7 is already in contact with the elastomer element 2 in the unactuated starting position, and the overall characteristic curve of the simulator unit 1 therefore has no linear section. Fig. 7

[0058] Fig. 4 shows an example of a constructive way to adjust the axial distance L by using different variants 5a, 5b of the closure cover with different axial heights Sa, Sb.

[0059] In this method, the closure cap is pressed flush with the surrounding surface of the housing 101. The different heights Sa and Sb cause the end surfaces 12a and 12b, which serve as piston stop surfaces, to be located in different axial positions. This also changes the initial position of the piston 7. Because the position of the elastomer element 2 is not affected, the axial distance between the piston 7 and the elastomer element changes.

[0060] Reference sign

[0061] 1 simulator unit

[0062] 2 elastomeric element

[0063] 3 Cavity

[0064] 4 simulator chambers

[0065] 5 sealing caps

[0066] 6. Borehole bottom

[0067] 7 pistons

[0068] 8 containers

[0069] 9 spring element

[0070] 10 Master cylinder unit

[0071] 11. Pressure chamber

[0072] 12 End surface

[0073] 13 Piston rod

[0074] Level 14

[0075] 15 bundles

[0076] 16 Radial canal

[0077] 17 Piston crown

[0078] 18 Survey

[0079] 19 Connection channel

[0080] 20 Drainage channel

[0081] 21 Sealing sleeve

[0082] 22 shut-off valve

[0083] 23 shaft

[0084] 24 guide surface

[0085] 25 Cutting edge

[0086] 26 Wide section

[0087] 27 Narrow section

[0088] 100 brake device

[0089] 101 cases

[0090] B Actuating force

[0091] G Counterforce

[0092] L Axial distance

[0093] S Height of the closure lid

Claims

Patent claims 1. Simulator unit (1 ) for generating a counterforce (G) acting against an actuating force (B) for a brake device (100) of a hydraulic vehicle brake system, comprising at least one piston (7) received in a simulator chamber (4), which can be moved from an unactuated initial position by hydraulic actuation and acts on at least one spring element (9) when moved, characterized in that the spring element (9) surrounds the piston (7) radially outside at least section by section.

2. Simulator unit (1) according to claim 1, characterized in that the simulator chamber (4) comprises at least one cavity (3) formed in a housing (101) in which the piston (7) is received at least partially and the spring element (9) is supported on the piston (7) and on the housing (101).

3. Simulator unit (1 ) according to claim 2, characterized in that the spring element (9) is designed as a helical spring.

4. Simulator unit (1 ) according to claim 3, characterized in that the cavity (3) is designed as a stepped bore with at least one step (14) which is provided for supporting the spring element (9).

5. Simulator unit (1 ) according to at least one of claims 2 to 4, characterized in that the piston (7) has at least one radially outwardly extended collar (15) which is provided for supporting the spring element (9).

6. Simulator unit (1) of claim 4, characterized in that the collar (15) is designed to guide and radially support the piston (7) in the cavity (3).

7. Simulator unit (1 ) according to at least one of the preceding claims, characterized in that the simulator chamber (4) is closed with a closure cover (5) and at least one piston-side end surface (12) of the closure cover (5) is provided as a stop for the piston (7) in its unactuated starting position.

8. Simulator unit (1 ) according to claim 7, characterized in that the piston (7) rests in its unactuated starting position at a defined axial distance (L) to an elastomer member (2), wherein the distance (L) is adjustable by adjusting the axial position of the end surface (12).

9. Simulator unit (1 ) according to at least one of the preceding claims, characterized in that the simulator chamber (4) is supplied with a hydraulic pressure medium via at least one radially opening connecting channel (19) and at least one radial channel (16) is provided for transferring the hydraulic pressure medium from a radially distal to a radially proximal area of ​​the simulator chamber (4), which is effective at least in the unactuated starting position of the piston (7).

10. Simulator unit (1 ) at least according to claims 7 and 9, characterized in that the radial channel (16) is formed as at least one radial recess in an edge region of the closure cover (5).

11. Simulator unit (1 ) at least according to claims 7 and 9, characterized in that the radial channel (16) is formed as at least one radial recess in an edge region of the piston (7).

12. Simulator unit (1) according to at least one of the preceding claims, characterized in that the piston (7) is designed as a thin-walled deep-drawn part.

13. Brake device (100) comprising at least one simulator unit (1) according to at least one of the preceding claims.

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