Compact simulator unit for a hydraulic brake device

Abstract

The invention relates to a hydraulic 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 linearly displaced from an unactuated initial position by hydraulic actuation (Fh) and, during displacement, acts on at least one elastomer element (2) via an intermediate element (12). To shorten the axial length and reduce the number of installed components, the invention proposes that the intermediate element (12) be designed as a radially elastic spring bushing, which converts the axial movement of the piston (7) into a radial dimensional change of the intermediate element (12).

Description

[0001] 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.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] A well-known and widely used design of a simulator unit is, for example, known 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.

[0006] After the hydraulic actuation force is removed, the pistons are returned to their unactuated starting position by the built-up spring tension. Disadvantages of this design include its large overall length and the tendency for the intermediate piston and spring element to become misaligned, tilted, or even tilted. This occurs due to floating bearings and / or the inherently limited radial guidance and support of the intermediate piston and spring element. As a result, undesirable wall contact can occur during operation, leading to noise and increased wear.

[0007] The object of the invention is therefore to propose an improved simulator unit which avoids the shortcomings of the prior art.

[0008] 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.

[0009] The invention provides that the intermediate element is designed as a radially elastic spring bushing, which converts the axial movement of the piston into a radial dimensional change of the intermediate element. The elastomeric element can be designed in an annular shape and radially enclose the intermediate element on the outside.

[0010] This significantly reduces the axial length of the simulator unit. Furthermore, the radially directed spring action forces components to self-center during operation. The elastomer element provides effective vibration damping and support in both radial and axial directions, resulting in improved noise characteristics.

[0011] Furthermore, the invention claims a braking device with at least one simulator unit according to the invention.

[0012] Further features and advantages of the invention will become apparent from the following description. The following were shown: Fig. 1 An exemplary braking device in a highly simplified internal structure view. Fig. 2 Axial section of an embodiment of the simulator unit in an unactuated initial state. Fig. 3. Simplified representation of the intermediate element in a side view. Fig. 4 Simplified representation of the intermediate member in axial section. Fig. 5 A selection of components of the simulator unit in exploded view. Fig. 1

[0013] Fig. Figure 1 shows an example of a brake-by-wire braking device 100 for a hydraulic braking system of a motor vehicle.

[0014] 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.

[0015] 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.

[0016] In the main cylinder unit 10, a pressure chamber 11 filled with a hydraulic pressure medium, for example brake fluid, is arranged. In the regular braking mode described above, the pressure chamber 11 is hydraulically connected to a simulator unit 1 instead of to one or more wheel brakes. In the embodiment shown, the simulator unit 1 is arranged in or on the housing 101 of the brake device 100.

[0017] A container 8 stores the hydraulic pressure medium and serves to supply the brake device 100 with it.

[0018] The simulator unit 1 comprises a simulator chamber 4, which in the embodiment shown is formed by a cavity 3 in the housing 101 and a pot-shaped closure cap 5 connected to the housing 101.

[0019] In the simulator chamber 4 there is a piston 7 which, when actuated, acts on a spring element 9 with a linear characteristic curve and on an intermediate member 12, as well as an elastomer member 2 with a progressive spring characteristic curve, which is actuated by the intermediate member 12.

[0020] When the main cylinder unit 10 is actuated, the hydraulic pressure medium is displaced from the pressure chamber 11 into the simulator unit 1 via a connecting channel 21, which can be closed off by means of a shut-off valve 25, and acts on the piston 7 therein. The piston 7 is thereby axially advanced against the spring force of the spring element 9. The intermediate member 12 is designed as a radially elastic spring bushing, which is radially stretched by the piston 7 during its translational displacement. This stretching action acts on an annular elastomer element 2, which bears radially outwards against the intermediate member 12 and also creates resistance to the translational advance of the piston. The radial stretching of the intermediate member 12 compresses and elastically deforms the elastomer element 2 between the intermediate member 12 and the inner surface of the cup-shaped end cap 5.The elastomeric element 2 exerts a radially inward force on the intermediate element 12 and via this on the piston 7.

[0021] A total resistance acting against the piston 7 during the actuation process in the simulator unit 1, resulting from the resistances of the spring element 9, the intermediate member 12 and the elastomer member 2, 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 the piston stroke depending on the design and construction of the simulator unit 1.

[0022] A sealing sleeve 22 sliding on the outer surface of the piston 7 separates the simulator chamber 4 into a wet area on the side of the connecting channel 21 from a dry area on the side of the elastomer element 2. Fig. 2

[0023] Fig. Figure 2 shows an embodiment of the simulator unit 1 according to the invention in an unactuated starting position in longitudinal section.

[0024] The housing 101 contains a cavity 3 designed as a blind bore, which accommodates the piston 7. The connecting channel 21 opens near the bottom of the cavity 3 into a kind of annular space 23, which radially surrounds the rear end of the piston 7. For better distribution of the pressure medium over the cross-section of the cavity 3, a shoulder 24 with a reduced diameter is formed on the piston 7, with which the piston 7 rests against the bottom of the cavity 3 in its initial position.

[0025] A spring element 9, designed as an axial helical spring, is clamped between the front face of the piston 7 and an end face 15 of the simulator chamber 4 formed by the base of the end cap. A separate receiving seat 16 is provided on the front face of the piston 7 for radial centering, support, and preferably also fastening of the spring element 9.

[0026] In the illustrated embodiment, a funnel-shaped circumferential collar 19 and a central narrowly tapered mandrel 20 are provided for this purpose, which encompass or preferably clamp at least the end coil of the spring element 9 radially on both sides.

[0027] Furthermore, the piston 7 has a section 6 on its side facing the intermediate member 12, which tapers towards the piston end and is conically shaped in the illustrated embodiment. The section 6 engages axially in the intermediate member 12 and, in the unactuated starting position, is located at a defined distance from the corresponding conical or funnel-shaped contact surface 14 of the intermediate member 12.

[0028] The intermediate member 12, which is axially supported at the front face 15, is designed as a radially elastic spring bushing, which, through the axial sliding of the conical section 6 on the funnel-shaped contact surface 14, converts the axially directed movement of the piston 7 into a circumferential change of the intermediate member 12 and thus a radial movement.

[0029] The elastomeric member 2 is essentially ring-shaped or tubular and is arranged on the radially outer surface of the intermediate member 12, for example elastically stretched over it.

[0030] When actuated, the piston 7 is moved axially from its initial position shown here towards the intermediate member 12 by hydraulic pressure until the conical section rests against the contact surface 14. In this first phase of the piston stroke, only the spring element 9 is compressed.

[0031] In the second phase, during the continued piston stroke, the conical section 6 of the piston 7 slides further into the intermediate member 12 at the conical contact surface 14, expanding it radially. The intermediate member 12 is thereby elastically tensioned. The annular elastomer element 2, attached to the outer circumference of the intermediate member 12, is thus stretched circumferentially and simultaneously compressed radially between the outer surface of the intermediate member 12 and the inner surface of the end cap 5.

[0032] When the hydraulic load is removed, the process reverses – the elastomeric element 2 and the intermediate element 12 contract radially, the contact surface 6 slides off the conical section 6, so that the piston 7 is forced out of the intermediate element 12. The spring element 9 then returns the piston 7 to its unactuated starting position. Figs. 3 and 4

[0033] Fig. 3 and Fig. Figure 4 shows a simplified embodiment of the intermediate member 12 in a side view or in an axial section.

[0034] The intermediate member 12 has a substantially tubular base body 17, made of metal or plastic, in which axial recesses 18, 18' are arranged alternately around the circumference to provide radial elasticity to opposing axial end faces. The intermediate member 12 can preferably be made of a fracture- and wear-resistant material with excellent sliding properties, for example polyethylene, brass, or similar materials. Fig. 5

[0035] Fig. Figure 5 shows an exploded view of the closure cap 5, the elastomer element 2 to be inserted therein and the intermediate element 12, as well as the piston with the characteristic conically tapered section 6. Reference sign 1 simulator unit 2 elastomeric element 3 Cavity 4 simulator chambers 5 Cap 6 tapering section 7 pistons 8 containers 9 spring element 10 Master cylinder unit 11. Pressure chamber 12 Intermediate link 13 Piston rod 14 Contact area 15 Front 16 Recording seat 17 basic shapes 18 recess 19th Federal Government 20 Dorn 21 Connection channel 22 Sealing sleeve 23 annular space Paragraph 24 25 shut-off valve 100 brake device 101 cases B Actuating force G Counterforce

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 linearly displaced from an unactuated initial position by a hydraulic actuation (Fh) and, when displaced, acts on at least one elastomeric element (2) via an intermediate element (12), characterized by , that the intermediate member (12) is constructed as a radially elastic spring bushing which converts the axial movement of the piston (7) into a radial dimensional change of the intermediate member (12). [2] Simulator unit (1) according to claim 1, characterized by , that the elastomeric member (2) is designed in a ring-shaped or tubular form and radially surrounds the intermediate member (12) on the outside. [3] Simulator unit (1) according to claim 1 or 2, characterized by, that the piston (7) has on its side facing the intermediate member (12) a tapered section (6) which engages axially in the intermediate member (12) and cooperates therein with a separate contact surface (14). [4] Simulator unit (1) according to claim 3, characterized by , that the contact surface (14) is conical or funnel-shaped. [5] Simulator unit (1) according to at least one of the preceding claims, characterized by , that an axially acting spring element (9) is arranged between the piston (7) and an end face (15) of the simulator chamber (4), wherein the piston (7) and the end face (15) serve as abutments for the spring element (9). [6] Simulator unit (1) according to claim 5, characterized by , that the spring element (9) is a helical spring which is configured as a compression spring. [7] Simulator unit (1) according to claim 6, characterized by, that the piston (7) has a receiving seat (16) which is designed to center the spring element (9) and to radially support at least one coil of the spring element (9). [8] Simulator unit (1) according to at least one of the preceding claims, characterized by , that the intermediate member (12) has a substantially tubular base body (17) made of metal or plastic, in which axial recesses (18, 18') are arranged alternately around the circumference to achieve radial elasticity from opposing axial end faces. [9] Simulator unit (1) according to claim 8, characterized by , that the simulator chamber (4) is limited by a cavity (3) formed in a housing (101) of the brake device (100) and a cup-shaped closure cap (5) connected to the housing (101) and at least the elastomer member (2) with the intermediate member (12) are arranged in the closure cap (5). [10] Braking device (100) comprising at least one simulator unit (1) according to at least one of the preceding claims.

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