Piston-cylinder device for a vehicle braking system and manufacturing method for a piston-cylinder device for a vehicle braking system

Abstract

Piston-cylinder device (50) for a braking system of a vehicle with a first piston (58) which is arranged in an internal volume (56) formed in the piston-cylinder device (50) and which is adjustable within the internal volume (56) against at least a first spring force of at least a first spring (60) with a first spring constant such that a first partial volume (56a) of the internal volume (56) which can be filled with brake fluid via at least a first bore (62) can be increased and a second partial volume (56b) of the internal volume (56) which can be filled with brake fluid via at least a second bore (64) can be decreased; wherein the piston-cylinder device (50) comprises at least a second spring (68) with a second spring constant smaller than the first spring constant of the first spring (60); characterized by a second piston (66) which is adjustable from at least one position of the second piston (66), in which the second piston (66) projects at least partially into the first partial volume (56a) of the internal volume (56), relative to the first piston (58) against at least a second spring force of at least the second spring (68), whereby the second piston (66) can be pushed out at least partially from the first partial volume (56a) of the internal volume (56).

Description

[0001] The invention relates to a piston-cylinder device for a vehicle's braking system. The invention also relates to a hydraulic unit for a vehicle's braking system and a braking system for a vehicle. Furthermore, the invention relates to a manufacturing method for a piston-cylinder device for a vehicle's braking system and a manufacturing method for a hydraulic unit for a vehicle's braking system. State of the art

[0002] Fig. 1a and Fig. Figure 1b shows a cross-section through a conventional pedal stroke simulator and a coordinate system to explain its operation.

[0003] The in Fig. Figure 1a shows a schematic representation of a conventional pedal stroke simulator installed in the Toyota Prius III. The conventional pedal stroke simulator has a housing consisting of a cast part 10 and a cover 12 inserted into the cast part 10. An internal volume within the housing is divided into a first sub-volume 14 and a second sub-volume 16 by means of an adjustable piston 18. The adjustable piston 18 carries an elastomer seal 20 and is supported by two simulator springs 22 and 24 arranged in the second sub-volume 16. The first simulator spring 22 of the two simulator springs 22 and 24 has a significantly lower spring stiffness than the second simulator spring 24 of the two simulator springs 22 and 24. The second simulator spring 24, which contacts the cover 12, pushes a spring plate 26 away from the cover 12.The piston 18 is pushed away from the inner surface of the spring plate 26 by means of the first simulator spring 22, which contacts an inner surface of the spring plate 26.

[0004] Brake fluid, which is forced out of a master brake cylinder connected to the conventional pedal stroke simulator by means of a driver braking force, can be transferred into the first partial volume 14 via a connecting bore 28 formed in the casting 10. Furthermore, a volume compensation opening 30 is formed in the casting 10, through which brake fluid from the second partial volume 16 can be transferred into a connected expansion tank.

[0005] Using the coordinate system of Fig. Figure 1b illustrates the functionality of a conventional pedal stroke simulator. An abscissa of the coordinate system of the Fig. Figure 1b specifies an adjustment travel s (in millimeters) of a brake actuation element (brake pedal) connected (via the master brake cylinder) to the conventional pedal stroke simulator. Using the ordinates of the coordinate system of Fig. 1b represents the driver braking force F (in Newtons) to be applied and the resulting pressure p (in bar) in the conventional pedal stroke simulator.

[0006] When a driver applies the brakes by actuating the brake actuator (brake pedal) in the conventional pedal stroke simulator, starting from a response force F0 and a response travel s0, the piston 18 first moves from the first partial volume 14 into the second partial volume 16, deforming the first simulator spring 22 until the piston 18 abuts the inner surface of the spring plate 26, with an adjustment travel s equal to a predetermined free travel Δs. If the driver continues to apply the brakes in the conventional pedal stroke simulator after the piston 18 has abutted the inner surface of the spring plate 26, the piston 18 and spring plate 26 are pushed towards the sealing piston 12, deforming the second simulator spring 24. The driver can use the driver's braking force F to push the piston 18 into the second partial volume 16 so far that an elastomer component 32 attached to the closure cover 12 is deformed.In this way, a force-displacement characteristic F(s) and a pressure-displacement characteristic p(s) with a large force or pressure increase at the end of the adjustment range s should be achievable for the conventional pedal stroke simulator. Furthermore, a hysteresis ΔF and Δp for the force-displacement characteristic F(s) and the pressure-displacement characteristic p(s) respectively should be ensured by means of the elastomer seal 20 surrounding the piston 18. The elastomer seal 20 causes static friction between the piston 18 and the housing, which the driver must overcome by means of a breakaway force Fa before any adjustment movement of the piston 18.

[0007] DE 10 2014 215 065 A1 discloses a piston for a piston-cylinder device in which part of the piston is elastically compressible.

[0008] In DE 10 2014 215 091 A1, a piston component of a simulator device of a brake system is disclosed, wherein at least one brake fluid path is designed in the piston component such that, if the adjustment travel of the piston component is greater than the limit adjustment travel, brake fluid from the second partial volume can be transferred via the at least one brake fluid path into the at least one second bore.

[0009] In DE 10 2011 006 746 A1 a brake system with a master brake cylinder is disclosed, wherein a spring force during an expansion of the spring device can be transferred to a piston of the master brake cylinder in such a way that the piston can be adjusted at least partially into an inner chamber of the master brake cylinder by means of the spring force.

[0010] In DE 10 2013 200 424 A1, a master brake cylinder for a vehicle's braking system is disclosed, wherein the internal volume of the master brake cylinder has two sub-areas and is designed in such a stepped manner that the first sub-area of ​​the internal volume has a first cross-sectional area perpendicular to the axis of the cylinder, which is smaller than a second cross-sectional area of ​​the second sub-area of ​​the internal volume perpendicular to the axis. Disclosure of the invention

[0011] The invention provides a piston-cylinder device for a vehicle braking system with the features of claim 1, a hydraulic unit for a vehicle braking system with the features of claim 10, a vehicle braking system with the features of claim 11, a manufacturing method for a piston-cylinder device for a vehicle braking system with the features of claim 12, and a manufacturing method for a hydraulic unit for a vehicle braking system with the features of claim 16. Advantages of the invention

[0012] The present invention enables the attachment of at least one sealing element to the first piston without the sealing element attached to the first piston impairing the breakaway force for adjusting the second piston. Therefore, at the start of a driver's braking action in the piston-cylinder device according to the invention, the second piston can be adjusted without applying a (significant) breakaway force, allowing a volume of brake fluid to be transferred into the first partial volume of the internal volume of the piston-cylinder device. The piston-cylinder device according to the invention thus has a jump-in working range that is free of breakaway force. The driver, who engages the piston-cylinder device according to the invention by actuating their brake actuator (brake pedal), therefore experiences an improved brake feel (pedal feel).The present invention thus contributes to increasing braking comfort for the driver.

[0013] For example, the second piston can be supported against at least one housing component by means of at least the second spring and can be adjusted, at least partially, against at least the force of at least the second spring, from the first partial volume of the internal volume into an internal volume of the housing. By means of such support of the second piston (directly) against the housing component / housing, the jump-in working range on the piston-cylinder device can be easily configured.

[0014] In another advantageous embodiment of the piston-cylinder device, the second piston is supported against the first piston by means of at least the second spring and is at least partially adjustable against at least the second spring force from the first partial volume of the internal volume into an internal volume of the piston spanned by the first piston. The first piston can thus fulfill multiple functions as both a piston component and a container component, thereby minimizing the size of the piston-cylinder device.

[0015] Preferably, the second piston is sealed against the first partial volume of the internal volume by means of a rolling diaphragm attached to the housing component or the first piston. The breakaway force required to at least partially push the second piston out of the first partial volume of the internal volume is therefore (almost) zero.

[0016] In a further advantageous embodiment, the piston-cylinder device comprises a spring plate and a stop pin projecting through an opening in a base region of the spring plate, wherein a stop pin head is located in a volume enclosed by the spring plate, wherein the first piston, with the second piston supported against the first piston by means of at least the second spring, is attached to an end of the stop pin pointing away from the stop pin head, and wherein the first spring is clamped between the first piston and a flange of the spring plate. The first piston and the second piston can thus be easily installed in the piston-cylinder device as components of the assembly described here in a few steps.In particular, the assembly can be checked for its characteristic curve and configured to a desired target characteristic curve before installation in the piston-cylinder device.

[0017] In particular, the first spring can be pre-tensioned by means of the insertion depth of the end of the stop pin pressed into the second piston. Furthermore, manufacturing tolerances can be compensated for in this way. Thus, a less precise first spring can also be used to manufacture the assembly without any disadvantages in the finished piston-cylinder device. Therefore, a cost-effective spring type can also be used for the first spring.

[0018] In an advantageous further development of the piston-cylinder device, an elastomer disc is inserted between the spring plate and at least one adjacent housing component. The elastomer disc ensures a smoother transition of the force required to adjust the first piston.

[0019] In a further advantageous embodiment, an elastically compressible part, through which the stop pin protrudes, is attached to a side of the first piston facing the spring plate. Upon contact between the elastically compressible part and the base of the spring plate, a counterforce opposing the elastic compression of the part prevents further compression of the spring plate and the first piston. The piston-cylinder device equipped with the elastically compressible part thus exhibits a force-volume characteristic curve that displays high force values ​​when a large volume is displaced into the first partial volume of the internal volume.

[0020] For example, the piston-cylinder device can be a simulator device. Due to its advantageous force-volume characteristic when braking a driver into the piston-cylinder device, it is particularly well-suited as a simulator device. However, it should be noted that the trainability / usability of the piston-cylinder device is not limited to a simulator device such as a pedal stroke simulator and / or a pedal travel simulator.

[0021] The piston-cylinder device can be designed as a component with its own housing. However, the advantages described above are also realized in a hydraulic unit for a vehicle's braking system that incorporates at least one such piston-cylinder device.

[0022] Likewise, the advantages described above are guaranteed for a braking system for a vehicle with at least one such piston-cylinder device or a corresponding hydraulic unit.

[0023] The implementation of a corresponding manufacturing process for a piston-cylinder device for a vehicle's braking system also yields the advantages described above. It should be noted that the manufacturing process for a piston-cylinder device can be further developed according to the embodiments of the piston-cylinder device explained above.

[0024] Furthermore, the advantages described above can also be ensured by implementing a corresponding manufacturing process for a hydraulic unit for a vehicle's braking system. For the sake of completeness, it should be noted that the manufacturing process for a hydraulic unit according to the piston-cylinder device embodiments described above can also be further developed. Brief description of the drawings

[0025] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1a and Fig. 1b a cross-section through a conventional pedal stroke simulator and a coordinate system to explain its operation; Fig. 2a to 2e schematic partial and overall representations of an embodiment of the piston-cylinder device; Fig. 3 a schematic representation of an embodiment of the braking system; and Fig. 4 a flowchart to explain an embodiment of the manufacturing process for a piston-cylinder device for a vehicle braking system. Embodiments of the invention

[0026] Fig. Figures 2a to 2e show schematic partial and overall representations of an embodiment of the piston-cylinder device.

[0027] The by means of the Fig. The piston-cylinder device 50 shown in 2a to 2e can be used in a vehicle's braking system. It should be noted that the applicability of the piston-cylinder device 50 is not limited to a specific type of braking system or vehicle. The piston-cylinder device 50 is shown here only as an example. Fig. Figures 2a to 2e show a device with its own housing consisting of a housing part 52 and a closure cover 54. However, the designability of the housing of the piston-cylinder device 50 is not limited to the one shown in Figures 2a to 2e. Fig. The components 52 and 54 shown in 2b to 2e are limited. Furthermore, the piston-cylinder device 50 (without its own housing) can also be integrated at least once into a hydraulic unit for a vehicle's braking system.

[0028] In the embodiment of the Fig. 2a to 2e, the piston-cylinder device 50 is a simulator device 50, or a simulator with its own housing consisting of the housing part 52 and the closure cover 54. Due to the force-volume characteristic curve of the piston-cylinder device 50 (or pressure-volume characteristic curve of the piston-cylinder device 50), which is described in more detail below, it can be advantageously used as a simulator device 50. However, it should be noted that the usability of the piston-cylinder device 50 is not limited to this purpose.

[0029] The housing of the piston-cylinder device 50 (comprising the housing part 52 and the sealing cap 54) has an internal volume 56. A first piston 58 is arranged within this internal volume 56. The first piston 58 is adjustable within the internal volume 56 against at least one first spring force of at least one spring 60 with a first spring constant, such that a first partial volume 56a of the internal volume 56, which can be filled with brake fluid via at least one first bore 62, can be enlarged. Furthermore, by adjusting the first piston 58 within the internal volume 56 against at least one spring force of at least one spring 60, a second partial volume 56b of the internal volume 56, which can be filled with brake fluid via at least one second bore 64, can be reduced.In particular, the first piston 58 can be arranged adjustably between the first partial volume 56a located on a first side of the first piston 58 and the second partial volume 56b of the inner volume 56 of the piston-cylinder device 50 located on a second side of the first piston 58 directed away from the first side.

[0030] The piston-cylinder device 50 can be connected to a (not shown) master brake cylinder of the respective brake system such that brake fluid from the master brake cylinder can be forced into the first partial volume 56a of the inner volume 56 via the at least one first bore 62. Furthermore, the piston-cylinder device 50 can be connected to a (not shown) reservoir of the respective brake system such that, while the first partial volume 56a is being filled, brake fluid from the second partial volume 56b of the inner volume 56 can be transferred into the reservoir via the at least one second bore 64. A driver can thus, by actuating a brake actuation element (brake pedal) connected to the master brake cylinder, apply the brake fluid to the piston-cylinder device 50 via the master brake cylinder.

[0031] The piston-cylinder device 50 also has a second piston 66, which, in at least one position, projects into the first partial volume 56a of the inner volume 56. From this position, where the second piston 66 projects at least partially into the first partial volume 56a, it is adjustable relative to the first piston 58 against at least one second spring force (at least one second spring 68 with a second spring constant), thereby allowing the second piston to be pushed out of the first partial volume 56a of the inner volume 56.

[0032] The second spring constant of the second spring 68 is smaller than the first spring constant of the first spring 60. A transfer of brake fluid via the at least one first bore 62 into the first partial volume 56a of the inner volume 56 thus initially causes a deformation of the second spring 68 with the smaller second spring constant, while the first spring 60 with the larger first spring constant remains (essentially) in its original shape. This creates a jump-in working range in the piston-cylinder assembly. The second piston 66 and the second spring 68 can therefore also be described as a jump-in piston and a jump-in spring, respectively. The piston-cylinder assembly 50 can thus also be used to simulate the jump-in working range. The driver, who engages the piston-cylinder assembly 50 by actuating the brake actuator (brake pedal), thus experiences a standard brake feel (pedal feel).

[0033] At least one seal 70, such as a lip seal 70, can be installed in the first piston 58. This ensures that, before the first piston 58 is moved from its current position, the sealing friction of the at least one seal 70 must be overcome by means of a comparatively high breakaway force. For example, the at least one seal 70 is installed in at least one groove 71, which is formed on a side of the first piston 58 facing a wall of the housing of the piston-cylinder device 50.

[0034] In contrast, the second piston 66 is preferably seal-free. Therefore, no sealing friction opposes any adjustment movement of the second piston 66 from its current position. Consequently, (virtually) no breakaway force is required before the second piston 66 can be adjusted from its current position. This is particularly advantageous because adjustment of the second piston 66 occurs within the jump-in operating range / at the beginning of braking into the piston-cylinder assembly 50 (or at the beginning of pressure build-up in the first partial volume 56a). Typically, during the jump-in operating range, the driver finds the sudden need to apply a large braking force (to overcome the sealing friction conventionally required for piston adjustment) irritating / disturbing.By means of the seal-free design of the second piston 66, an improved brake actuation feel (pedal feel) is created, especially within the jump-in working range for the driver braking into the piston-cylinder device 50.

[0035] Simultaneously, the at least one seal 70 installed on the first piston 58 ensures that the force-volume characteristic of the piston-cylinder device 50 (or pressure-volume characteristic of the piston-cylinder device 50) exhibits perceptible hysteresis outside the jump-in operating range. This can also be described as the force-volume characteristic of the piston-cylinder device 50 (or pressure-volume characteristic of the piston-cylinder device 50) exhibiting perceptible hysteresis as soon as the first piston 58 (equipped with the at least one seal 70) begins to move. Within the jump-in working range / before the adjustment of the first piston 58, the force-volume characteristic of the piston-cylinder device 50 (or pressure-volume characteristic of the piston-cylinder device 50) is, however, (almost) hysteresis-free. Thus, in contrast to the prior art, the piston-cylinder device 50 exhibits a force-pressure characteristic (or pressure-volume characteristic of the piston-cylinder device 50).a pressure-volume characteristic curve) whose perceptible hysteresis only occurs when the volume filled into the first partial volume 56a exceeds a limit volume.

[0036] The occurrence of a noticeable hysteresis in the force-volume characteristic curve of the piston-cylinder device 50 (or pressure-volume characteristic curve of the piston-cylinder device 50) from the limit volume onwards prevents the release of the connected brake actuation element (brake pedal) after heavy braking from immediately triggering a change in a previously requested vehicle deceleration. Likewise, due to the hysteresis of the force-volume characteristic curve of the piston-cylinder device 50 (or pressure-volume characteristic curve of the piston-cylinder device 50) from the limit volume onwards after the release of the brake actuation element, it is ensured that re-actuation / re-engagement does not trigger an overly immediate effect of the deceleration. A "nervous" brake actuation feel (pedal feel) is therefore reliably prevented when braking into the piston-cylinder device 50 with a volume above the limit volume.Furthermore, when braking into the piston-cylinder device 50 with a volume above the limiting volume, the driver hardly perceives a large breakaway force as disturbing.

[0037] In the embodiment of the Fig. 2a to 2e are coil springs, the first being spring 60 and the second spring 68. However, it should be noted that other spring types can also be used for the first spring 60 and / or the second spring 68.

[0038] For example, the embodiment of the Fig. 2a to 2e, the second piston 66 is disengaged from the first piston 58 by means of at least the second spring 68. The second piston 66 is adjustable, at least partially, against at least the second spring force of at least the second spring 68, from the first partial volume 56a of the internal volume 56 into an internal piston volume 72 opened up by the first piston. The first piston 58 thus fulfills both a piston function and a receiving container function. By means of this multifunctionality of the first piston 58, the piston-cylinder device 50 can be minimized.

[0039] The second piston 66 (or the piston's internal volume 72) is sealed against the first partial volume 56a of the internal volume 56 by means of a rolling diaphragm 76 attached to the first piston 58. The rolling diaphragm 76 can be stretched on a side of the second piston 66 facing away from the first piston 58, with the rolling diaphragm 76 being attached to the first piston 58, for example, by means of a retaining ring 78.

[0040] To advantageously support the second piston 66 against the first piston 58 by means of at least the second spring 68, the second spring 68 can first be inserted, at least partially, into a spring-receiving opening 79 formed on the first piston 58 such that a first side of the second spring 68 contacts the first piston 58. The second piston 66 can then be at least partially placed over the spring-receiving opening 79 such that a second side of the second spring 68, facing away from the first side, projects into a volume enclosed by the second piston 66. The second piston 66 can then be pressed into the piston's internal volume 72, and the rolling diaphragm 76 can be attached to the first piston 58 by means of the retaining ring 78 on a side of the second piston 66 facing away from the piston's internal volume 72. The retaining ring 78 can be pressed or welded into the first piston 58.

[0041] In an alternative embodiment, the second piston 66 can also be supported against at least one housing component of the piston-cylinder device 50 by means of at least the second spring 68. In this case, the second piston 66 is adjustable, at least partially, against at least the second spring force of at least the second spring 68, from the first partial volume 56a of the inner volume 56 into an inner volume of the housing (formed in the piston-cylinder device 50). In this case as well, the second piston 66 and / or the inner volume of the housing can be sealed against the first partial volume 56a of the inner volume 56 by means of a rolling diaphragm 76.

[0042] In the embodiment of the Fig. 2a to 2e, the first piston 58 and the second piston 66, which is supported on the first piston 58 by means of at least the second spring 68, are part of an assembly (subassembly) 80. The first spring 60 and the second spring 68 are also clamped in the assembly 80. For this purpose, the assembly 80 has a spring plate 82 and a stop pin 84 projecting through an opening in a base region of the spring plate 82. (The stop pin 84 holds the various components of the assembly 80 together.) A stop pin head 84a of the stop pin 84 lies in a volume enclosed by the spring plate 82. The first piston 58 is attached to an end 84b of the stop pin 84 that points away from the stop pin head 84a.During an adjustment movement of the first piston 58 in relation to the spring plate 82, the stop pin head 84a of the stop pin 84 is therefore pressed from the bottom area of ​​the spring plate 82 towards a spring plate edge surrounded by a flange of the spring plate 82.

[0043] The first spring 60 is clamped between the first piston 58 and the flange of the spring plate 82. The spring plate 82 thus projects at least partially into a volume enclosed by the coils of the first spring 60. The stop pin 84 is also at least partially surrounded by the coils of the first spring 60. Preferably, the end 84b of the stop pin 84, which points away from the stop pin head 84a, is pressed into the first piston 58, with the first spring 60 being preloaded by a pressing depth Δx of the end 84b of the stop pin 84 pressed into the first piston 58. In particular, manufacturing tolerances of the first spring 60 can be compensated for by means of the preload. Thus, a cost-effective spring type can also be used for the first spring 60.

[0044] The in Fig. The enlarged assembly 80 (pre-assembly) shown in Figure 2a can be tested before being installed in the piston-cylinder device 50. Furthermore, a subsequent characteristic curve of the piston-cylinder device 50 can be determined by varying the press-fit depth Δx. This allows the assembly 80 to be optimized, particularly with regard to its later use as a simulator assembly 80.

[0045] The further training offered by the [profession] is advantageous. Fig. The assembly 80 shown in Figure 2a includes an elastically compressible part 86, which is attached to a side of the first piston 58 facing the spring plate 82 and through which the stop pin 84 projects. Once the elastically compressible part 86 comes into contact with the base of the spring plate 82, further movement of the first piston 58 towards the base of the spring plate 82 causes the elastically compressible part 86 to compress. Therefore, to achieve a large volume in the first partial volume 56a of the internal volume 56, a counterforce opposing the elastic compression of the part 86 must be overcome in addition to at least the first spring force of the first spring 60. A force-volume characteristic / pressure-volume characteristic of the piston-cylinder device 50 equipped with the elastically compressible part 86 therefore exhibits comparatively high force / pressure values ​​for a large volume in the first partial volume 56a.

[0046] In the embodiment of the Fig. In sections 2b to 2e, an additional elastomer disc 88 is inserted between the spring plate 82 and at least one adjacent housing component 54 of the piston-cylinder assembly 50, such as the end cap 54. This ensures a smooth transition of the first piston 58 from its various positions.

[0047] The following section will explain the functionality of the piston-cylinder device 50 once again: As a rule, the first partial volume 56a of the internal volume 56, which can be filled with brake fluid, is minimal before the brake actuating element (brake pedal) interacting with the piston-cylinder assembly 50 is actuated. Once the brake actuating element (brake pedal) is actuated, the driver can apply pressure to the piston-cylinder assembly 50 via the master brake cylinder, which first pushes the second piston 66 out of the first partial volume 56a by deforming the second spring 68. The second piston 66 is thus moved into the piston's internal volume 72 by rolling the diaphragm 76. Since only the second spring 68 opposes the resulting increase in the first partial volume 56a, the operation of the piston-cylinder assembly 50 corresponds to a jump-in behavior.

[0048] It should be noted that no sealing friction opposes the adjustment of the second piston 66 relative to the first piston 58. The adjustment of the second piston 66 relative to the first piston 58 can therefore occur even at a comparatively low pressure in the first partial volume 56a, without having to overcome a breakaway force.

[0049] If brake fluid is present within the piston's internal volume 72 before the brake actuation element (brake pedal) is applied, it can escape into the volume enclosed by the spring plate 82 via a first fluid channel 90a formed in the first piston 58 and / or a second fluid channel 90b extending through the stop pin 84. The brake fluid can then be transferred from the internal volume of the spring plate 28 to the reservoir via at least one second bore 64.

[0050] Once the brakes engage the piston-cylinder assembly 50, which has a volume equal to the limiting volume, the second piston 66 strikes the first piston 58. After the second piston 66, which has been pushed out of the first partial volume 56a, has reached this point, brake fluid is forced further into the first partial volume 56a by adjusting the first piston 58, which deforms the first spring 60. The limiting volume can therefore also be described as the jump-in volume. To further engage the piston-cylinder assembly 50 by adjusting the first piston 58, the sealing friction of the at least one seal 70 installed on the first piston 58 must first be overcome. This is perceptible as a pressure point. However, any corresponding increase in the driver's braking force can be "washed away" by means of the elastomer disc 88.By using different Shore hardnesses and Shore thicknesses for the elastomer disc 88, the various vehicle applications can be taken into account.

[0051] By increasing the first partial volume 56a during an adjustment movement of the first piston 58, the first piston 58 approaches the spring plate 82. Once the elastically compressible part 86, attached to the first piston 58, contacts the spring plate 82, a further increase in the first partial volume 56a by further adjustment of the first piston 58 is only possible through elastic compression of the elastically compressible part 86. In this way, it is ensured that a large driver braking force is required to compress a comparatively large volume into the first partial volume 56a. A characteristic of the piston-cylinder device 50 thus corresponds to that of a standard braking system. Furthermore, different hardnesses and lengths can be used for the elastically compressible part 86, which can be described as an elastomer spring. A progressive partial curve of the force-volume characteristic (or...)the pressure-volume characteristic curve) can thus be adapted to a desired characteristic of the piston-cylinder device 50.

[0052] Fig. Figure 3 shows a schematic representation of one embodiment of the braking system.

[0053] The in Fig. Figure 3, a schematically depicted brake system, features two piston-cylinder devices 50 as simulator devices 50. (Each simulator device 50 can be a separate component or integrated into a hydraulic unit of the vehicle brake system.) The two simulator devices 50 can optionally be connected to at least one pressure chamber of a master brake cylinder 102 via a simulator valve 100 and / or a check valve 104. Furthermore, the simulator devices 50 are connected to a reservoir / brake fluid reservoir 108 of the brake system via at least one suction line 106. By connecting several simulator devices 50 in parallel to the master brake cylinder 102, the stroke length occurring at each simulator device 50 can be shortened during a driver's braking maneuver.The number of parallel simulator devices (50) can be freely selected. The brake system's equipment... Fig. Figure 3, with exactly two simulator devices 50, is merely an example. Even with a braking system equipped with only one simulator device 50, a braking feel (pedal feel) acceptable to the user can be generated with a specially tuned characteristic curve.

[0054] The braking system of the Fig. Figure 3 has, for example, two brake circuits 110a and 110b. Each brake circuit 110a and 110b has two wheel brake cylinders 112, one wheel inlet valve 114 per wheel brake cylinder 112, and one wheel outlet valve 116 per wheel brake cylinder 112. Each brake circuit 110a and 110b is connected to the master brake cylinder 102 via a first isolating valve 118. Furthermore, each brake circuit 110a and 110b is connected via a second isolating valve 120 to a motorized piston-cylinder device 122 (e.g., a plunger). After closing the respective first isolating valve 118, the brake pressure present in the wheel brake cylinders 112 of the respective brake circuit 110a or 110b can be adjusted independently of an actuation of a brake actuation element / brake pedal 124 connected to the master brake cylinder 102 by means of the motorized piston-cylinder device 122.Furthermore, the brake system can have at least one pre-pressure sensor 126 and / or at least one pressure sensor 128. Optionally, the brake system can also be equipped with at least one brake actuation sensor 130, e.g., a pedal travel sensor and / or a rod travel sensor 130.

[0055] Fig. Figure 4 shows a flowchart to explain one embodiment of the manufacturing process for a piston-cylinder device for a vehicle braking system.

[0056] The manufacturing process described below can be used, for example, to produce the piston-cylinder device embodiment explained above. However, the feasibility of the manufacturing process is not limited to this type of piston-cylinder device.

[0057] In process step S1, a first piston is supported within an internal volume of the subsequent piston-cylinder assembly by means of at least one first spring with a first spring constant such that the first piston is adjustable against at least one first spring force. By adjusting the first piston against at least one spring force, a first partial volume of the internal volume, which can be filled with brake fluid via at least one first bore (and is bounded by a first side of the first piston), is increased, and a second partial volume of the internal volume, which can be filled with brake fluid via at least one second bore (and is bounded by a second side of the first piston opposite the first side), is decreased.

[0058] In a process step S2, performed before, simultaneously with, or after the first step, a second piston is supported by at least a second spring with a second spring constant smaller than the first spring constant of the first spring, such that the second piston, in at least one position, projects at least partially into the first partial volume of the internal volume. Furthermore, it is ensured that the second piston, from this at least one position relative to the first piston, can be adjusted against at least one second spring force, thereby transferring the second piston at least partially out of the first partial volume of the internal volume.For example, the second piston can be supported on the first piston by means of at least the second spring in such a way that the second piston can be adjusted, at least partially, against at least the force of the second spring, from the first partial volume of the internal volume into an internal volume of the piston spanned by the first piston. Likewise, the second piston can also be supported on at least one housing component of the piston-cylinder assembly.

[0059] In an advantageous further development of the manufacturing process, a process step S01 is performed before process steps S1 and S2: In process step S01, a stop pin is at least partially pushed through an opening in a base region of a spring plate such that the head of the stop pin lies within a volume enclosed by the spring plate. Subsequently, the first piston is attached to an end of the stop pin pointing away from the head of the stop pin, with the first spring being clamped between the first piston and a flange of the spring plate.

[0060] Optionally, a process step S02 can be added to process steps S1 and S2 after process step S01: In process step S02, the first spring is pre-tensioned by pressing the end of the stop pin into the first piston. By defining a press-in depth for the end of the stop pin pressed into the second piston, the pre-tension of the first spring can also be set to a desired value. Furthermore, in an optional process step S03, which can be performed as an alternative to process step S02, either before or after process step S02, the assembly / sub-assembly formed in process step S01 can be checked for its characteristic curve.

[0061] The manufacturing process described here thus offers all the advantages already described above. Furthermore, process steps S01 to S03, S1 and S2 can also be used to integrate at least one piston-cylinder device into a hydraulic unit of a brake system.

Claims

[1] Piston-cylinder device (50) for a braking system of a vehicle with a first piston (58) which is arranged in an internal volume (56) formed in the piston-cylinder device (50) and which is adjustable within the internal volume (56) against at least a first spring force of at least a first spring (60) with a first spring constant such that a first partial volume (56a) of the internal volume (56) which can be filled with brake fluid via at least a first bore (62) can be increased and a second partial volume (56b) of the internal volume (56) which can be filled with brake fluid via at least a second bore (64) can be decreased; wherein the piston-cylinder device (50) comprises at least a second spring (68) with a second spring constant smaller than the first spring constant of the first spring (60); characterized by a second piston (66) which is adjustable from at least one position of the second piston (66), in which the second piston (66) projects at least partially into the first partial volume (56a) of the internal volume (56), relative to the first piston (58) against at least a second spring force of at least the second spring (68), whereby the second piston (66) can be pushed out at least partially from the first partial volume (56a) of the internal volume (56). [2] Piston-cylinder device (50) according to claim 1, wherein the second piston (66) is supported by means of at least the second spring (68) on at least one housing component (52) of the piston-cylinder device (50) and is adjustable at least partially against at least the second spring force of at least the second spring (68) from the first partial volume (56a) of the inner volume (56) into an inner volume of the housing. [3] Piston-cylinder device (50) according to claim 1, wherein the second piston (66) is supported on the first piston (58) by means of at least the second spring (68) and is adjustable at least partially against at least the second spring force of at least the second spring (68) from the first partial volume (56a) of the internal volume (56) into a piston internal volume (72) opened up by the first piston (58). [4] Piston-cylinder device (50) according to claim 2 or 3, wherein the second piston (66) is sealed against the first partial volume (56a) of the internal volume (56) by means of a rolling diaphragm (76) attached to the housing component (52) or the first piston (58). [5] Piston-cylinder device (50) according to claim 3 or 4, wherein the piston-cylinder device (50) comprises a spring plate (82) and a stop pin (84) projecting through an opening in a base region of the spring plate (82), wherein a stop pin head (84a) of the stop pin (84) is located in a volume enclosed by the spring plate (82), wherein the first piston (58) is attached to the second piston (66) which is supported on the first piston (58) by means of at least the second spring (68) at an end (4b) of the stop pin (84) facing away from the stop pin head (84a), and wherein the first spring (60) is clamped between the first piston (58) and a flange of the spring plate (82). [6] Piston-cylinder device (50) according to claim 5, wherein the first spring (60) is pre-tensioned by means of a press-in depth (Δx) of the end (84b) of the stop pin (84) pressed into the first piston (60). [7] Piston-cylinder device (50) according to claim 5 or 6, wherein an elastomer disc (88) is inserted between the spring plate (82) and at least one adjacent housing component (54) of the piston-cylinder device (50). [8] Piston-cylinder device (50) according to one of claims 5 to 7, wherein an elastically compressible part (86) through which the stop pin (84) protrudes is attached to a side of the first piston (58) oriented towards the spring plate (82). [9] Piston-cylinder device (50) according to any of the preceding claims, wherein the piston-cylinder device (50) is a simulator device (50). [10] Hydraulic unit for a braking system of a vehicle comprising at least one piston-cylinder device (50) integrated therein according to one of the preceding claims. [11] Braking system for a vehicle comprising at least one piston-cylinder device (50) according to any one of claims 1 to 9 or a hydraulic unit according to claim 10. [12] Manufacturing process for a piston-cylinder device (50) for a braking system of a vehicle comprising the steps: Supporting a first piston (58) by means of at least a first spring (60) with a first spring constant within an internal volume (56) of the subsequent piston-cylinder device (50) such that the first piston (58) is adjustable against at least a first spring force of at least the first spring (60) in such a way that a first partial volume (56a) of the internal volume (56) which can be filled with brake fluid via at least a first bore (62) is increased and a second partial volume (56b) of the internal volume (56) which can be filled with brake fluid via at least a second bore (64) is decreased (S1); wherein at least a second spring (68) with a second spring constant smaller than the first spring constant of the first spring (60) is arranged on the piston-cylinder device (50); characterized by the step: Supporting a second piston (66) with at least the second spring (68) such that the second piston (66) in at least one position of the second piston (66) projects at least partially into the first partial volume (56a) of the internal volume (56) and is adjustable from the at least one position relative to the first piston (58) against at least a second spring force of at least the second spring (68), whereby the second piston (66) is transferred at least partially out of the first partial volume (56a) of the internal volume (56) (S2). [13] Manufacturing method according to claim 12, wherein the second piston (66) is supported on the first piston (58) by means of at least the second spring (68) in such a way that the second piston (66) is adjustable at least partially against at least the second spring force of at least the second spring (68) from the first partial volume (56a) of the internal volume (56) into a piston internal volume (72) opened up by the first piston (58). [14] Manufacturing method according to claim 13, wherein a stop pin (84) is pushed at least partially through an opening in a base region of a spring plate (82) such that a stop pin head (84a) of the stop pin (84) lies in a volume enclosed by the spring plate (82), wherein the first piston (58) is attached to an end (84b) of the stop pin (84) pointing away from the stop pin head (84a), and wherein the first spring (60) is clamped between the first piston (58) and a flange of the spring plate (82) (S01). [15] Manufacturing method according to claim 14, wherein the first spring (60) is pre-tensioned by pressing the end (84b) of the stop pin (84) into the first piston (58) (S02). [16] Manufacturing method for a hydraulic unit for a braking system of a vehicle, wherein at least one piston-cylinder device (50) is integrated into the hydraulic unit by means of one of the methods according to claims 12 to 15.

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