Device for use in a braking system for a motor vehicle

Abstract

Device (1) for use in a braking system for a motor vehicle, wherein the device (1) has a housing (2) designed as a tandem master cylinder and wherein a piston (3) is designed as the piston of the tandem master cylinder, comprising a housing (2) with a housing outer surface (22) and a housing inner space (21), a piston (3) which can be inserted through an opening into the housing (2) and is linearly movable in the housing inner space (21), and a sensor arrangement (8) designed to detect a position of the piston (3), characterized in that the housing (2) has a slot (7) extending between the housing inner space (21) and the housing outer surface (22), in which at least a part of the sensor arrangement (8) is arranged.

Description

[0001] The present invention relates to a device for use in a braking system for a motor vehicle according to the preamble of claim 1.

[0002] To generate brake pressure in hydraulic brake systems, a master brake cylinder or tandem master brake cylinder is used. It contains a linearly movable piston that is actuated by a brake pedal. The corresponding movement or position of the piston pressurizes the brake fluid to actuate a brake actuator.

[0003] It is known that non-contact sensors can be used to monitor the position of the piston. For example, a powerful permanent magnet carried along with the piston can serve as a transmitter element for a sensor element and map the position of the piston with its position. The permanent magnet acts magnetically through the housing of the master brake cylinder, which can be made of aluminum, for example, onto a magnetic-inductive linear position sensor. The simple mechanical integration of the position-sensing permanent magnet results in low design effort with this measuring principle. However, the use of a magnetic-inductive sensor is negatively affected by its excessive sensitivity to external magnetic interference fields, as this can sometimes be associated with considerable effort on the sensor side for shielding and sensor design.

[0004] Purely inductive sensors do not exhibit such sensitivity to external magnetic interference fields. A position sensor can be implemented, for example, using a simple metal sheet. Due to its electrical conductivity, eddy currents change the inductance of a coil, thus indicating its position and thus the position of the piston. However, the effect of the position sensor cannot overcome the normally metallic housing of the master brake cylinder, as is the case with a magnetic-inductive sensor. Eddy currents associated with the high excitation frequencies of the purely inductive sensor system thwart this. Accordingly, considerable mechanical design effort is required to bypass the housing wall when guiding the sensor element, ensuring that no metallic part interferes with the measurement.

[0005] It is therefore an object of the present invention to provide a device for use in a braking system for a motor vehicle which is space-saving and / or requires little construction effort.

[0006] The object is achieved according to the invention by a device for use in a braking system for a motor vehicle, comprising a housing with a housing outer side and a housing interior, a piston which can be pushed through an opening into the housing and is mounted for linear movement in the housing interior, and a sensor arrangement which is designed to detect a position of the piston, wherein the housing has a slot which extends through the housing interior and the housing outer side and in which at least part of the sensor arrangement is arranged. The fact that at least part of the sensor arrangement is arranged in the slot is preferably understood to mean that at least one component is arranged completely or partially in the slot or projects into the slot.The advantage of the slotted sensor arrangement is that a sensor element of the sensor arrangement can be positioned directly near a transmitter element of the sensor arrangement with a very small air gap. Alternatively, the slotted sensor arrangement allows the transmitter element to be guided along a sensor element on the outside, thus separated from the pressure inside the housing, without loss of installation space. This is possible, for example, with a suitable mount.

[0007] The invention preferably also relates to a sensor arrangement, wherein a sensor element is fixedly fastened to a housing of a piston, wherein the sensor element is designed to measure a position of a transmitter element, wherein the transmitter element is fastened to the piston and wherein the housing has a slot extending between the housing interior and the housing exterior, in which slot the sensor element and / or the transmitter element is arranged.

[0008] Advantageous embodiments of the invention are the subject of the dependent claims. The wording of the claims is incorporated into the description by express reference.

[0009] Preferably, the sensor arrangement comprises the following components: - a sensor element fixed to the piston, or a sensor element fixed to a holder, the holder being fixed to the piston, and - a sensor element fixedly attached to the housing. Such a sensor arrangement is inexpensive and well-suited for use in a motor vehicle braking system. At least one of these components, but possibly several, can partially penetrate the slot or completely traverse it.

[0010] The sensor element preferably comprises a coil, in particular a planar coil, wherein the coil is designed and arranged such that its inductance depends on or is influenced by the position of the sensor element. Such a measuring principle is easy to implement and cost-effective.

[0011] According to a preferred embodiment, the coil of the sensor element is formed from conductor tracks of an electrical circuit for detecting the inductance and outputting an inductance-dependent signal. In this way, the planar coil can be applied directly to the circuit simply by forming the conductor tracks. This saves production and material costs, since neither a separate coil needs to be purchased nor applied to the circuit in a separate manufacturing step. The coil is preferably designed as a planar coil and integrated into the electrical circuit.

[0012] According to a further preferred embodiment, the coil of the sensor element is part of a measuring transformer comprising a second coil and an excitation coil, wherein the excitation coil is designed to induce an electrical alternating voltage in the two coils. The sensor element is designed to detect the influence on the induced alternating voltage of at least one of the two coils by the transmitter element or by a magnetic saturation induced by the transmitter element in a soft magnetic core and to output a signal dependent thereon by means of an electrical circuit. The influence on the induced alternating voltage preferably corresponds to a phase shift or change in the voltage.

[0013] The sensor element is preferably made of an electrically conductive and / or ferromagnetic material. With a purely inductive measuring principle, in which the change in the coil's inductance is directly measured as a result of the influence of a ferromagnetic and / or electrically conductive sensor element, the negative influence of interference fields on the measurement is minimized.

[0014] It is preferred that the sensor element is designed as a variation of the piston diameter in the direction of movement and / or as an edge, in particular an end edge, of the piston and / or as an annular, in particular magnetically encoded, piston attachment.

[0015] According to a further preferred embodiment, the holder comprises a rod and a web, in particular one that is formed integrally therewith, wherein the sensor element is fastened to the rod, which is rigidly connected to the web fastened to one end of the piston, wherein the web projects into or through the slot. Thus, the rod extends the effective range of the sensor element in the direction of movement of the piston towards the housing. This allows the sensor element to be arranged at a structurally more advantageous location, further away from the opening. Furthermore, the distance between the sensor element and the sensor element can be adjusted as desired. The web, together with the rod, can accordingly have an L-shape.

[0016] Preferably, the slot is designed such that the rod and / or the web are slidably mounted in the slot in the direction of movement. Accordingly, the slot forms a linear sliding bearing for the rod and / or the web. This allows the movement path or positioning of the encoder element to be precisely defined and ensured.

[0017] It is preferred that the sensor element, together with an electrical circuit for processing and outputting signals from the sensor element, be enclosed in a sensor housing with a plug connection. The sensor arrangement can be contacted or signals can be output via the plug connection. The sensor housing can be designed to ensure sealing of the slot. With appropriate design, it can contribute to the mechanical stability and strength of the housing.

[0018] It is preferred that the slot extends from the housing opening in the direction of movement of the piston, in particular from a side of the housing facing away from the pressure. The housing opening can also be formed in a housing part that forms a mounting flange for the rest of the housing. The fact that the slot extends from the opening or is arranged at the end edge of the housing has the advantage that the influence of the slot on the rigidity of the housing, in particular on the opening, is minimized.

[0019] It is preferred that the housing interior has a region with a lower pressure, preferably approximately the ambient pressure of the housing, and a region with a higher pressure, wherein the regions are separated in particular by a seal, with the slot extending only in the region with a lower pressure. Due to this arrangement or design, the slot has little influence on the tightness and strength of the housing.

[0020] Preferably, the slot is formed in a recess in the housing. This allows the sensor housing to be easily and space-savingly attached to the device housing.

[0021] Preferably there is insulation between the transmitter element and the sensor element.

[0022] Preferably, the housing is designed as a tandem master brake cylinder and the piston as a piston of a tandem master brake cylinder.

[0023] Preferably, the housing is divided into a first and a second housing part, which are designed in particular as separable components, wherein the first housing part forms a fastening flange for the second housing part and wherein the slot extends along the entire first housing part in the direction of movement of the piston.

[0024] The invention is explained in more detail below with reference to exemplary embodiments and drawings. They show, in schematic form: Fig. 1 shows a device according to the invention according to a first embodiment, Fig. 2 a device according to the invention according to the first embodiment in a spatial partially sectioned view, Fig. 3 a device according to the invention according to the first embodiment from a different spatial perspective, Fig. 4 a device according to the invention according to the first embodiment in a further spatial partially sectioned view, in which the sensor housing is also shown, Fig. 5 a device according to the invention according to a second embodiment, Fig. 6 a device according to the invention according to the second embodiment in a further view,

[0025] The Fig. The device 1 shown in Figure 1 for use in a braking system for a motor vehicle has a housing 2 designed as a tandem master brake cylinder. It further has a piston 3 or pressure piston, which is arranged to be movable in one direction of movement in the housing 2, wherein the movement of the piston 3 can be controlled by a foot pedal (not shown). For this purpose, the foot pedal is connected to a coupling rod 4, which is designed to transmit the force exerted on the foot pedal to one end of the piston 3 and thus set it in motion. The position of the piston 3 is detected by a sensor arrangement 8.

[0026] The piston 3 itself is divided into a primary piston 31 and a secondary piston 32, with the primary piston 31 closing an opening in the housing 2 and the secondary piston 32 dividing the interior of the housing 2 into a primary chamber and a secondary chamber. In the area of ​​the opening in the housing 2, a secondary sleeve 52 is arranged on the primary piston 31, which isolates a housing interior 21 from the ambient air. Viewed into the housing interior 21, after the secondary sleeve 52 follows a primary sleeve 51, which seals a gap between the primary piston 31 and a wall of the housing 2. A pressure sleeve on the secondary piston 32 isolates the pressure in the primary chamber from the pressure in the secondary chamber. Furthermore, another primary sleeve 51 on the secondary piston 32 seals a gap between the secondary piston 32 and the wall of the housing 2.

[0027] The primary piston 31 is supported against the secondary piston 32 by a first spring, while the secondary piston 32 is supported against a housing base by a second spring. The primary chamber and the secondary chamber can be supplied with hydraulic fluid (not shown) via a first and second connection, respectively.

[0028] The housing 2 includes a mounting flange 6 on the side with the opening for positioning the coupling rod 4 and for tightly fastening the rest of the housing 2, so that the opening is only open to the coupling rod 4 and the piston 3, but not to the outside. The mounting flange 6 rests against the rest of the housing 2 in the axial direction, i.e. in the direction of movement of the piston 3, and in the radial direction. It has a slot 7 or gap in the direction of movement of the piston 3, which exposes the piston 3 lying below in the housing interior 21. The slot 7 continues into the rest of the housing 2 so far that the total gap length approximately corresponds to the stroke length of the piston 3.

[0029] The sectional view of the Fig. Figure 2 shows the interaction of the mounting flange 6 with the remaining housing 2, with the slot 7 extending through the entire mounting flange 6 as well as part of the remaining housing 2. Parts of the piston 3 are not shown in this and other figures, or are shown transparently, to allow a clear view of, for example, the coupling rod 4 as well as springs and sealing sleeves.

[0030] Slot 7 is easier to see in Fig. 3. To reduce mechanical stresses, the slot 7 is rounded at the end. The housing 2, in particular the wall thickness of the housing 2 and the slot 7, are dimensioned such that the housing 2 can withstand the pressures in the housing interior 21 and that sufficient rigidity of the opening of the housing 2 is ensured, thus enabling precise guidance of the piston 3.

[0031] Fig. 4 again shows a sectional view, but this time with a housed sensor element 82. This sensor housing 84 is partially arranged and secured in a recess 23 of the housing 2, which partially surrounds the slot 7. The sensor element 82 itself, or rather the part of the sensor housing 84 that surrounds it, is arranged in the slot 7. The side walls of the sensor housing part that surrounds the sensor element 82 rest firmly against the side walls of the slot 7. A seal can also be provided here.

[0032] The arrangement of the sensor element 82 in the slot 7 enables the position of the piston 3 to be measured without the wall of the housing 2 getting in the way, or distorting or making the measurement impossible. In this exemplary embodiment, the position of the piston 3 is represented by a sensor element 81 in the form of a ring. This can be ferromagnetic and / or have a magnetic coding. A number of measuring principles for detecting the position are known to those skilled in the art, for example, measurement using one or more Hall elements. The ring can be pressed into a circumferential groove of the piston 3 or glued or screwed to the piston 3. However, a differently shaped attachment can also be used instead of the ring. A specific geometry of the piston 3, for example, the end edge of the piston 3 on the side of the opening in the housing 2, can also form the sensor element 81 for detecting the position of the piston 3.

[0033] Depending on the design of the sensor element 81, certain measuring principles may be advantageous. If the sensor element 81 has electrically conductive properties, as is the case with aluminum or copper, for example, the inductance of a coil 83 of the sensor element 82 can be changed by eddy currents. If the sensor element 81 has ferromagnetic properties, as is the case with soft iron, for example, the inductance of a coil 83 of the sensor element 82 can be changed by changing its magnetic properties. The coil 83, not shown in this figure, is designed as a coil wound on a coil body and / or core, but can also be designed as a planar coil to save space. The coil 83 or the sensor element 82 is electrically connected to an electrical circuit for processing and outputting signals, which can be contacted via a plug connection of the sensor housing 84.

[0034] In the Fig. 5, the slot 7 is provided according to a further embodiment instead of for the sensor element 82, as in the embodiment of Fig. 4, can also be used for the sensor element 81. For this purpose, a holder 9 is attached to the end of the piston 3, which emerges from the opening of the housing 2 upon corresponding movement of the piston 3.

[0035] The holder 9 has a web 91 protruding radially from the piston 3. In the exemplary embodiment, this is formed as a single piece with a sleeve or collar around the piston 3, which sleeve can be secured, for example, by a press fit. The web 91 merges into a rod 92, which carries the sensor element 81 at its end. The rod 92 with the sensor element 81 extends on the outer side 22 of the housing, i.e., the outside of the housing wall, so that the sensor element 82 can also be arranged outside the housing wall. When the piston 3 moves, only the web 91 moves in the slot 7, while the rod 92 with the sensor element 81 is moved outside the housing wall. The holder 9 and the slot 7 are designed in such a way that the web 91 does not come to a stop at the end of the slot 7 when the transmitter element 81 has reached the end of the coil 83 of the sensor element 82, which occurs when the total stroke of the piston 3 is reached.Coil 83 of sensor element 82 is designed as a planar coil and is therefore very flat and space-saving. It is covered by the sensor element 81 at a specific point depending on its position, causing its inductance to change. This is detected and evaluated in an electrical circuit as an indicator of the position of piston 3.

[0036] In Fig. 6 clearly shows how the coil 83 of the sensor element 82 is arranged above the slot 7 in the recess 23 of the housing 2 to detect the position of the transmitter element 81. A sensor housing 84, which surrounds the coil 83 and also contains the electrical circuit, is not shown so that the coil 83 and the holder 9 can be seen more clearly.

[0037] If it becomes apparent during the proceedings that a feature or group of features is no longer absolutely necessary, the applicant will now endeavor to formulate at least one independent claim that no longer includes the feature or group of features. This may, for example, be a subcombination of a claim existing on the filing date or a subcombination of a claim existing on the filing date that is limited by additional features. Such newly formulated claims or combinations of features are to be understood as being covered by the disclosure of this application.

[0038] It should also be noted that configurations, features, and variants of the invention described in the various embodiments and / or shown in the figures can be combined with one another as desired. Individual or multiple features are interchangeable. Resulting feature combinations are to be understood as being covered by the disclosure of this application.

[0039] References in dependent claims are not to be understood as a waiver of independent, objective protection for the features of the referenced subclaims. These features can also be combined with other features as desired.

[0040] Features that are disclosed only in the description, or features that are disclosed in the description or in a claim only in conjunction with other features, can in principle be of independent, essential significance to the invention. They can therefore also be included individually in claims to distinguish them from the prior art.

Claims

[1] Device (1) for use in a brake system for a motor vehicle, wherein the device (1) has a housing (2) which is designed as a tandem master brake cylinder and wherein a piston (3) is designed as a piston of the tandem master brake cylinder, comprising a housing (2) with a housing outer side (22) and a housing interior (21), a piston (3) which can be pushed through an opening into the housing (2) and is mounted in the housing interior (21) for linear movement, and a sensor arrangement (8) which is designed to detect a position of the piston (3), characterized by that the housing (2) has a slot (7) extending between the housing interior (21) and the housing exterior (22), in which slot at least part of the sensor arrangement (8) is arranged. [2] Device (1) according to claim 1, characterized by that the sensor arrangement (8) comprises the following components: - a sensor element (81) which is fastened to the piston (3), or a sensor element (81) which is fastened to a holder (9), wherein the holder (9) is fastened to the piston (3), and - a sensor element (82) which is fixedly fastened to the housing (2). [3] Device (1) according to claim 2, characterized by that the sensor element (82) comprises a coil (83), in particular a planar coil, wherein the coil (83) is designed and arranged such that its inductance depends on the position of the transmitter element (81). [4] Device (1) according to claim 3, characterized by that the coil (83) of the sensor element (82) is formed from conductor tracks of an electrical circuit for detecting the inductance and for outputting a signal dependent on the inductance. [5] Device (1) according to claim 3 or 4, characterized byin that the coil (83) of the sensor element (82) is part of a measuring transformer having a second coil (83) and an excitation coil, wherein the excitation coil is designed to induce an electrical alternating voltage in the two coils (83), wherein the sensor element (82) is designed to detect the influence on the induced alternating voltage of at least one of the two coils (83) by the transmitter element (81) or by a magnetic saturation caused by the transmitter element (81) in a soft magnetic core and to output a signal dependent thereon by means of an electrical circuit. [6] Device (1) according to one of claims 2 to 5, characterized by that the sensor element (81) consists of an electrically conductive and / or ferromagnetic material. [7] Device (1) according to claim 6, characterized bythat the sensor element (81) is designed as a variation of the piston diameter in the direction of movement and / or as an edge, in particular an end edge, of the piston (3) and / or as an annular, in particular magnetically encoded, piston attachment. [8] Device (1) according to one of claims 2 to 6, characterized by that the holder (9) comprises a rod (92) and a web (91), in particular formed in one piece therewith, wherein the transmitter element (81) is fastened to the rod (92), which is rigidly connected to the web (91) fastened to one end of the piston (3), wherein the web (91) projects into the slot (7). [9] Device (1) according to claim 8, characterized by that the slot (7) is designed such that the rod (92) and / or the web (91) is slidably mounted in the slot (7) in the direction of movement. [10] Device (1) according to one of the preceding claims, characterized bythat the sensor element (82) together with an electrical circuit for processing and outputting signals from the sensor element (82) is surrounded by a sensor housing with a plug connection. [11] Device (1) according to one of the preceding claims, characterized by that the slot (7) extends from the opening of the housing (2) in the direction of movement of the piston (3). [12] Device (1) according to one of the preceding claims, characterized by that the housing interior (21) has, in relation to one another, a region with lower pressure, in particular ambient pressure of the housing (2), and a region with higher pressure, wherein the regions are separated by a seal, wherein the slot (7) extends only in the region with lower pressure. [13] Device (1) according to one of the preceding claims, characterized by that the slot (7) is formed in a recess (23) of the housing (2). [14] Device (1) according to one of the preceding claims, characterized by that the housing (2) is divided into a first and a second housing part, which are designed in particular as separable components, wherein the first housing part forms a fastening flange (6) for the second housing part and wherein the slot (7) extends along the entire first housing part in the direction of movement of the piston (3).

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